Add initial session support

This works, but still needs tests.
Add session usage example
Merge branch 'master' into sessions

Includes the recent cookie-related changes, which are a key component of the
session handling.
Add cookie support into the session object
Add isset/unset to the session object
Update session phpdoc
Add basic tests for session handling
Add expanded session testing
Merge pull request #62 from rmccue/sessions

Add session support!