Added mongodb backend.
renamed package in mongobackend.go
Added tests for mongobackend

Copied sql tests almost exactly.
Added bson info to main auth file to make it work.
Reworded some test failure stuff.

Two tests failing.
added travis yml
setting up travis tests
Using proper travis database
Addresses issue #6. Fixed one test, just forgot to update code
fixed user update for mongodb

Addresses issue #7
All mongodb tests passing, but issue with delete

Deleting a user that doesn't exist fails the sql tests. This could be
good behavior, could be bad. Right now sql and mongo do different
things. Fixed the SaveUser stuff, may have added proper session closing.

Addresses issue #7
Rename mongobackend.go to mongoBackend.go
mongodb tests passing

figured out bug, I wasn't using the global backend in the tests.

Issue #6
Using Upsert in SaveUser. Closes issue #7
Added unique index on Username field for mongodb

really closes #7
Closes #8
Prevent error on close when mgo.Dial errors

minor comment on Issue #6
Added error for use when non-existant user is deleted

Implemented in mongoBackend. Addresses issue #9.
Raising error on deleting missing user for sql backend.

Issue #9
Raising error on deleting non-existant user for gobfile backend

Closes #9
deleteuser docs
mongobackend close docs
Added mongodb backend.