Add browser builds targeting es5 envs

[Andarist]

fixes #93

[Andarist]

Have no idea why appveyor fails at the moment - I thought that reading package.json might be the problem, but I've tested various forms:

• import pkg from './package.json'
• const pkg = require('./package.json')
• const pkg = JSON.parse(fs.readFileSync(path.resolve(__dirname, 'package.json'), 'utf8'));

There seems to be some error while loading config file, ain't sure how to debug this.

[adrianheine]

You could try bumping the rollup dependency.

[Andarist]

@adrianheine ok, tests are passing. I'm too used to using es6 goodness 😅 , but AppVeyor is configured for node@4, which doesnt support most of it (I guess it must be different node's version than in Travis as it worked there)

[adrianheine]

I'm good with this. @Rich-Harris could you have a quick look?

[adrianheine]

I just updated the rollup dependency and created merge conflicts here, sorry. Anyway, if you want to resolve them I'm gonna merge this.

[Andarist]

Done.

[adrianheine]

Thank you!

[Andarist]

Thanks for merging! any plans for releasing this any time soon?

[adrianheine]

I would like to do a release, maybe this week or next.

[adrianheine]

I just released 0.19.0.