Adjust to rubyzip 1.0 release (e.g. corrected incompatibilities)

* had to adjust one spec that relied on internal rubyzip structure
  that changed
* removed duplicated gem dependencies from Gemfile to use gemspec,
  development gem group probably should also be defined there
jbundler support
Recompile the booster jar after changes for "unsafe" bytes

These changes were made in 5bba9d3fff45786c26a591138660fe1c9858c728.
Reset RubyGems gemspec cache between tests

Fixes #203
Merge branch 'recompile' of github.com:shepmaster/warbler into shepmaster-recompile
updated name of bouncy_castle jars in require statements for runnable scripts for jruby1.7.5
converted integration tests to jruby 1.7.5 and the jruby-maven-plugin
Merge branch 'rubyzip_fix' of github.com:PragTob/warbler into PragTob-rubyzip_fix
added a comment to the Gemfile to explain why the warning messages are generated when using the gemspec directive
resolved some duplication between the Gemfile and the gemspec
updated readme with maven details
reverted an update to the rubyzip gem. will have to wait for another day.
trying to get the bullets in the readme to look right
Add some indirection when calling RubyZip

This will allow us to add alternate implementations, such as the one
provided by newer versions of RubyZip, or maybe a Java-powered one in
the future.
Support rubyzip 1.0

This adds a second zip adapter that uses the new API introduced by
rubyzip 1.0. Unfortunately, rubyzip 1.0 is no longer compatible with
Ruby 1.8, which warbler needs to support.

End users that wish to continue using warbler with a 1.8 interpreter
will need to prevent rubyzip 1.0 from being installed, such as by
using a pessimistic version constraint with Bundler.

To mimic this version constraint in the Travis environment, I had to
add a special 1.8 mode Gemfile to the Travis 1.8 builds.
updated history
added license to gemspec
upgrade integs to jruby 1.7.6, and fixed an rvm problem
added jruby 1.7.6 to travis build
testing maven in the travis config