fix(deps): update dependency koa to v2.8.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
koa	dependencies	minor	2.7.0 -> 2.8.1

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Release Notes

koajs/koa

### [`v2.8.1`](https://togithub.com/koajs/koa/blob/master/History.md#​281--2019-08-19) [Compare Source](https://togithub.com/koajs/koa/compare/2.8.0...2.8.1) ================== **fixes** - \[[`287e589`](http://github.com/koajs/koa/commit/287e589ac773d3738b2aa7d40e0b6d43dde5261b)] - fix: make options more compatibility (dead-horse >) ### [`v2.8.0`](https://togithub.com/koajs/koa/blob/master/History.md#​280--2019-08-19) [Compare Source](https://togithub.com/koajs/koa/compare/2.7.0...2.8.0) ================== **features** - \[[`5afff89`](http://github.com/koajs/koa/commit/5afff89eca0efe7081309dc2d123309e825df221)] - feat: accept options in the Application constructor ([#​1372](https://togithub.com/koajs/koa/issues/1372)) (Jake >) **fixes** - \[[`ff70bdc`](http://github.com/koajs/koa/commit/ff70bdc75a30a37f63fc1f7d8cbae3204df3d982)] - fix: typo on document ([#​1355](https://togithub.com/koajs/koa/issues/1355)) (Jeff >) **others** - \[[`3b23865`](http://github.com/koajs/koa/commit/3b23865340cfba075f61f7dba0ea31fcc27260ec)] - docs: parameter of request.get is case-insensitive ([#​1373](https://togithub.com/koajs/koa/issues/1373)) (Gunnlaugur Thor Briem >) - \[[`a245d18`](http://github.com/koajs/koa/commit/a245d18a131341feec4f87659746954e78cae780)] - docs: Update response.socket ([#​1357](https://togithub.com/koajs/koa/issues/1357)) (Jeff >) - \[[`d1d65dd`](http://github.com/koajs/koa/commit/d1d65dd29d7bbaf9ea42eaa5fcb0da3fb4df98e9)] - chore(deps): install egg-bin, mm as devDeps not deps ([#​1366](https://togithub.com/koajs/koa/issues/1366)) (Edvard Chen >) - \[[`2c86b10`](http://github.com/koajs/koa/commit/2c86b10feafd868ebd071dda3a222e6f51972b5d)] - test: remove jest and use egg-bin(mocha) ([#​1363](https://togithub.com/koajs/koa/issues/1363)) (Yiyu He >) - \[[`219bf22`](http://github.com/koajs/koa/commit/219bf22237b11bc375e2e110b93db512f1acfdd4)] - docs(context): update link ([#​1354](https://togithub.com/koajs/koa/issues/1354)) (Peng Jie >) - \[[`52a6737`](http://github.com/koajs/koa/commit/52a673703a87a93c0f6a8552e6bd73caba66d2eb)] - chore: ignore Intellij IDEA project files ([#​1361](https://togithub.com/koajs/koa/issues/1361)) (Imon-Haque >) - \[[`b9e3546`](http://github.com/koajs/koa/commit/b9e35469d3bbd0a1ee92e0a815ce2512904d4a18)] - docs(api): fix keygrip link ([#​1350](https://togithub.com/koajs/koa/issues/1350)) (Peng Jie >) - \[[`d4bdb5e`](http://github.com/koajs/koa/commit/d4bdb5ed9e2fe06ec44698b66c029f624135a0ab)] - chore: update eslint and fix lint errors (dead-horse >) - \[[`12960c4`](http://github.com/koajs/koa/commit/12960c437cc25c53e682cfe5bff06d74a5bb1eb9)] - build: test on 8/10/12 (dead-horse >) - \[[`00e8f7a`](http://github.com/koajs/koa/commit/00e8f7a1b7603aabdb7fb3567f485cb1c2076702)] - docs: ctx.type aliases ctx.response, not ctx.request ([#​1343](https://togithub.com/koajs/koa/issues/1343)) (Alex Berk >) - \[[`62f29eb`](http://github.com/koajs/koa/commit/62f29eb0c4dee01170a5511615e5bcc9faca26ca)] - docs(context): update cookies link ([#​1348](https://togithub.com/koajs/koa/issues/1348)) (Peng Jie >) - \[[`b7fc526`](http://github.com/koajs/koa/commit/b7fc526ea49894f366153bd32997e02568c0b8a6)] - docs: fix typo in cookie path default value docs ([#​1340](https://togithub.com/koajs/koa/issues/1340)) (Igor Adamenko >) - \[[`23f7f54`](http://github.com/koajs/koa/commit/23f7f545abfe1fb6499cd61cc8ff41fd86cef4a0)] - chore: simplify variable ([#​1332](https://togithub.com/koajs/koa/issues/1332)) (kzhang >) - \[[`132c9ee`](http://github.com/koajs/koa/commit/132c9ee63f92a586a120ed3bd6b7ef023badb8bb)] - docs: Clarify the format of request.headers ([#​1325](https://togithub.com/koajs/koa/issues/1325)) (Dobes Vandermeer >) - \[[`5810f27`](http://github.com/koajs/koa/commit/5810f279a4caeda115f39e429c9671795613abf8)] - docs: Removed Document in Progress note in Koa vs Express ([#​1336](https://togithub.com/koajs/koa/issues/1336)) (Andrew Peterson >) - \[[`75233d9`](http://github.com/koajs/koa/commit/75233d974a30af6e3b8ab38a73e5ede67172fc1c)] - chore: Consider removing this return statement; it will be ignored. ([#​1322](https://togithub.com/koajs/koa/issues/1322)) (Vern Brandl >) - \[[`04e07fd`](http://github.com/koajs/koa/commit/04e07fdc620841068f12b8edf36f27e6592a0a18)] - test: Buffer() is deprecated due to security and usability issues. so use the Buffer.alloc() instead ([#​1321](https://togithub.com/koajs/koa/issues/1321)) (Vern Brandl >) - \[[`130e363`](http://github.com/koajs/koa/commit/130e363856747b487652f04b5550056d7778e43a)] - docs: use 'fs-extra' instead of 'fs-promise' ([#​1309](https://togithub.com/koajs/koa/issues/1309)) (rosald >) - \[[`2f2078b`](http://github.com/koajs/koa/commit/2f2078bf998bd3f44289ebd17eeccf5e12e4c134)] - chore: Update PR-welcome badge url ([#​1299](https://togithub.com/koajs/koa/issues/1299)) (James George >)

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[coveralls]

Coverage remained the same at 80.638% when pulling b52c687fa6aed8eeecfd9408e2290472bedccc39 on renovate/koa-2.x into 1ab03ecde229708e7d30d478462b45a4ed612cd8 on master.