New Ruby filetypes

[Gavin Sinclair]

There are some new file categories on the scene that contain Ruby code
but don't end in .rb.  Is there anything we can do to get Vim to
recognise them as Ruby files, and to get the next Vim version to
recognise them automatically?  Is this desirable?

The files are:
  Rakefile       (Rake rules file)
  *.gemspec      (RubyGems specification file)
  *.gem          (RubyGems installation file - the result of executing
                  a .gemspec)

Gavin