Modify compiler to use ExecJS instead of TheRubyRacer directly
Update specs to be compatible with rspec ~> 3.1
Update specs to use ExecJS

Also modify includes/util.js to be compatible with node.js runtime
Update README

Add a note about node.js scope in inclusions
Merge pull request #5 from scarfacedeb/execjs

Replace TheRubyRacer with ExecJS