Adds og hook methods to track user membership on projects.

Also makes several infrastructural improvements to the project.  The silly filepath parameter has been removed from the post_request method and replaced with a check for a filestring at data['file'].  Adds OG as a dependency of tapas_transform, which is required for invoking og api hooks.  Implements a put_request method to be used with all TapasHydraConnector update requests and factors out a general purpose http_request method to be used to support the various verbs (get/put/post/delete) that the Rails repository knows what to do with.
Use isset to check if data['file'] is set

Without this, watchdog emits a notice that a nonexistent index is being
checked against the data array, which is annoying and noisy.  Given that
a NULL assignment to data['file'] should be ignored we don't have to do
further checking against the key.
Fixes two bugs with request_membership_update

Remove reference to nonexistent variable og_Membership (should be
og_membership) and call update_group instead of update_project, which
againt doesn't exist.  Dangers of committing before enough of the rails
app is written to actually test communication w. it in a meaningful way.