Updated the license file.
Removed trailing whitespace in the README.
Cleaned up the Gemspec.
First step in modernizing the project layout.

These changes are largely imported from Oga.
Restructured the whole project.

The following has been changed:

* The test suite has been migrated from Bacon to RSpec
* Tests now run on Travis
* Rake tasks have been cleaned up
* FFI code has been cleaned up