eslint is much more powerful and flexible than jshint, and we don't want
to promote writing new projects with pre-ES6 code.
As a side effect, this also avoids downloading PhantomJS (see
https://github.com/jshint/jshint/issues/3318), thereby cutting down
node_modules/ from 470 MB to 210 MB.
This makes sure we always include all files in the repository when
disting.
Obsoletes webpack-with-stats, which had a bug anyway: it wasn't
reporting jslint errors.
This moves us one step closer to a normal source package. The sources
are now unpacked and we run "make install". We still don't build
since we don't have all the necessary tools.
Also, most importantly, the source tarball now includes our actual
sources in addition to the prebuilt binaries.
