Highlight regexps after <<, +, -, and *

Closes #136.
Use s:Match instead of =~ to avoid matching strings or comments
Add symbols to string-like patterns
Fix incorrect match group reference

There can never be a second group here, as the regex only has one.
Support Ruby 2.0's prepend keyword

Which, for the most part, is just like include.
Correctly highlight identifiers with unicode characters

Ruby 2.0's default encoding is UTF-8, so these are now allowed by
default.
Revert "Add symbols to string-like patterns"

This reverts commit 9d16028720743e61a8078553d7d60b6d619d2ceb.
Add support for public_constant & private_constant (added in Ruby 1.9.3)
Highlight Ruby 2.0 symbol array syntax (%i)
Merge pull request #137 from amarshall/prepend-keyword

Add support for Ruby 2.0's prepend keyword
Merge pull request #140 from amarshall/constant-accessors

Add support for public_constant & private_constant (added in Ruby 1.9.3)
Merge pull request #141 from ngollan/ruby-2.0-symbol-arrays

Highlight Ruby 2.0 symbol array syntax (%i)
Remove "Anon CVS" headers
Add a rake compiler plugin

It always bugged me how the first match is almost always some irrelevant
stack trace line, or I would have added this years ago.
Introduce tests
Migrate an example to a spec
One more spec for issue #81
Spec
Tests for issue 130
Spec for issue 108