Upgrade JRuby to 1.7.6
Update warbler to 1.4.0.beta2 (addresses jruby/warbler#197)

See https://github.com/jruby/warbler/issues/197 for more
details. I was seeing the issue where additional null characters
were being added to the end of the web.xml files when
building the application.
Remove explicit inclusion of jruby-openssl
Don't let Warbler override our gems path (thanks @marktriggs)
Prevent JRuby 1.7.6.dev jars from being included in dist
Merge pull request #34 from anarchivist/jruby-1.7.6

Upgrade JRuby to 1.7.6