Rather than bundling, we're going to try adding an extension script to
manually install the correct version of listen.
Conflicts:
lib/sass/plugin/compiler.rb
lib/sass/util.rb
This opens the door for supporting recent versions of listen without
causing undue pain for users of Ruby 1.8.7 on Mac OS X. Listen
versions beyond 1.1 don't support Ruby 1.8.7, but this is installed by
default on many versions of OS X. Widening the version constraint on
listen is also unworkable, since RubyGems will try to select the most
recent version even if it's not compatible with the local Ruby
installation.
