Line numbers now display by default.
Update the version of the url module that browserify uses from npm.

This fixes things so that commands like:

  git grep --untracked --no-exclude-standard <pattern>

work again. As you can see from the comment in the code, we could
use a modern version of browserify if they would fix
https://github.com/substack/node-browserify/issues/796.
Fixed CSS generation so it matches the default "dark" theme in Atom.