Add note on how to build the jar and bundle
Add bundler development dependency

This allows you to run the command:

    bundle exec rake test

Before this change, this command failed with the error:
Gem::LoadError: rake is not part of the bundle. Add it to Gemfile.
Add Travis CI configuration file

Just enable Travis CI for this project and everything should work.
Add Travis CI badge to the top of the README
Consistenly use double quotes in Rakefile
Cleanup trailing whitespace