Remove libshadow-ruby1.8 package

We're using Ruby 1.9
ruby-shadow is included in omnibus

If we wanted to install it locally, say we didn't use Omnibus, then we need
to add some way to ensure we get ruby1.9+ install, per preference, as well
as the -dev package so we can compile the gem.
Merge pull request #17 from btm/fix_ruby_shadow

Fix ruby shadow