Adds linux support

This change allows the Big Red Button to work in Linux (I tested it in Ubuntu 2.04.1 LTS). Depending on the host OS, gem install automatically compiles an OSX or a Linux version of the gem.

I've updated the README.md with instructions.

I added a .gitignore to prevent committing garbage (compilation files, for example) in the future.

I decided not to touch author and version info in dream_cheeky.gemspec, to let you decide what to do.