Reorganize to allow for alternate datasources
Fix a couple small issues with graphite datasource
Fix graphite datasource
Removed deferred redrawing

It never worked as intended -- redraws would happen as soon as the refresh
method returned, not when all of the data had been updated.
Fix graph handling
Don't pass period to graphite datasource
Implement librato datasource
Merge pull request #64 from eric/backend-refactor

Reorganize to allow for alternate datasources