Update mocha to version 2.5.1 🚀

Hello :wave:

:rocket::rocket::rocket:

mocha just published its new version 2.5.1, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of mocha – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging :palm_tree:

The new version differs by 52 commits .

015b809 Release v2.5.1
3ef083e update CHANGELOG.md [ci skip]
bd9450b to-iso-string must be a dependency
30e917b Release v2.5.0
443697f rebuild mocha.js
9bfbc9e update CHANGELOG.md, contributors, .mailmap
524862b full browserification support; closes #880 (#2271)
9e8cbaa try different strategy for avoiding insecure sauce connect
f8a3d86 trying to fix travis + sauce check for PRs and forks
0dde0fa don't run SauceLabs tests on PRs
0b1e9b3 add more unit tests for various browsers
c04c1d7 Make CI run browser tests (#2231)
b76989c Add --icu-data-dir flag for node (#2248)
5e1439d Fix JSDoc (#2219)
3904da4 adds node 6 to CI matrix; closes #2239 (#2251)

There are 52 commits in total. See the full diff.

This pull request was created by greenkeeper.io. It keeps your software up to date, all the time.

_{Tired of seeing this sponsor message? Upgrade to the supporter plan!
You'll also get your pull requests faster :zap:}

Munter / tolk

Update mocha to version 2.5.1 🚀 #161