Use "babel-eslint" as parser for ESLint

[BR0kEN-]

With Babel we can use a lot of syntax sugar - it's cool, but ESLint ain't able to fit the things.

For instance, class properties aren't available. More information can be found here: babel/babel-eslint#312

[coveralls]

Coverage remained the same at 98.571% when pulling 36ed132 on BR0kEN-:feature/class-properties into c062a9e on coryhouse:master.

[coryhouse]

I'm torn on this. I took this out because it's only necessary for those running experimental features. But I totally understand why some would want to use them, so I'll go ahead and accept. Thanks for the PR. 👍