Move lib/snappy.{bundle,so} to lib/snappy_ext.{bundle,so}

Also remove the requires from the C code, and add a lib/snappy.rb that requires snappy_ext, snappy/writer and snappy/reader.
Ignore the build products in Git
Add Java support

Add a dependency on snappy-jars which contain Xerial's Snappy implementation for Java and code that implements a JRuby interface to that library. Also modify the Rakefile to build the JRuby extension, and a new .gemspec for the JRuby-compatible gem.
Use eval instead of load in snappy-jruby.gemspec

`load` doesn't work from Bundler, so `rake -T` broke. `eval` seems to be the way to do it from looking at how Bundler does it.
Fix the build and release tasks to do both MRI and JRuby

The build task will build both the MRI and JRuby gem, and the release task will release both gems. The combined install would fail, though, so it's not included.

The build task depends on lib/snappy_ext.jar to make sure that that file is included in the JRuby gem. It needs to be built from JRuby, but the build task doesn't have to be run from JRuby.
Find jruby.jar with rbconfig instead of RVM environment variable
Use a single gemspec instead of a JRuby specific

Also revert Gemfile and some features in Rakefile back to how they are in master.
Remove a stray debug message
Move the rbconfig require to the top of Rakefile
Make sure the load path is set up before compiling
Make sure the JAR is created just before a gem build
Merge pull request #8 from iconara/jruby_support

JRuby support