Reddit backend in django-social-auth only since 0.7.23
Clean up base requirements

Be a bit less strict with versions, we can always add upper version
limits when we actually see a problem with it.

times and logbook where useless since rq is/was depending on it.

httplib2 appears to be unused.
Add upper version limits for potentially breaking release

    * tastypie was reported to be broken in 0.9.16.
    * south 0.8 compatibility is untested right now.