WSGI now supports passing data in to tasks

Switched to using WebOb to help with WSGI - something wasn't working
right with my WSGI implementation, and why bother fixing it when there's
a perfectly good library I can use.
Fixed and tidied up GoogleAPI

Lease releasing wasn't working because @task_queue wasn't defined on the
protocol.  Also switched to using JSON.encode! rather than manually
pattern matching.
Tasks are now deleted after 5 retries.