Cleanup npm Tarball from Unnecessary Files

[nikitaeverywhere]

Hello! Thanks for a nice React component.

There are a lot of unnecessary files uploaded to NPM registry, check this:

This pull request adds some of them to .npmignore file and hence saves a bit of worldwide traffic 😄

Also this fixes Webpack trying to pick up .babelrc file and finding plugins that are not installed in the system.

src folder may also be excluded (as you build to lib), but I leave it up to your preference.

[coveralls]

Coverage remained the same at 98.551% when pulling a3808d5 on ZitRos:master into 58033e2 on alexcurtis:master.

[maximilianoforlenza]

#200