Optional SSL/TLS method specification for sandbox HTTP resource.
Remove DMTwitterTransport (we will be adding dm support to TwitterTransport instead)
Add move screen name utils back into TwitterTransport (now that DMTwitterTransport is gone)
Fix false positive twitter transport tests caused by `yield` (thanks @jerith)
Merge branch 'develop' of github.com:praekelt/vumi into develop
Merge branch 'develop' into feature/issue-739-dm-twitter-transport