add quotes around ubuntu

fixes: FATAL: NameError: undefined local variable or method `ubuntu'
update package list in default.rb

Substituted libreadline5 for libreadline5-dev and added libyaml-syck-perl.
Default recipe now works for 1.9.3-p194 under precise-server ubuntu when
run on vagrant (my scenario...), whereas it would die with libreadline5-dev,
as the server versions of ubuntu don't provide libreadline5-dev going back
through lucid(doh!) As using libreadline5 works just fine, seemed like the
right move (no special case logic...)
edit metadata.rb and README to reduce confusion for chef noobs (like me!)

I changed the references to the default recipe in metadata.rb and README.mdown to
be consistent with actual usage :)
add metadata for compatible with Librarian
fix json format for librarian
batting around in the dark here... sure would love some docs
update README for Berkshelf