Support query (and webpack 2)

[unimonkiez]

Hey, first of all thanks for the loader, been serving me for quite some time 👍 .

As of Webpack 2 adding properties to the main config is disallowed. Loaders are required to receive their config via queries. This pull request also solves issue #20 and the non existing issue which is to support webpack 2.

Already tested and works fine on my repo.

Thanks in advance, unimonkiez

[rodmax]

I just use this pull request in my setup with webpack2... It seems working :)

[unimonkiez]

@dianadumbravean Fixed README

[deepsweet]

there is no need to use isparta anymore, see https://github.com/deepsweet/istanbul-instrumenter-loader.

this one is deprecated and no longer maintained.