Stub out OutboundHelper
Test stubs for OutboundHelper
Move infer_addr_type out of contacts.dummy and into utils
Move format_addr out of contacts.dummy and into utils
Implement OutboundHelper (involved changing send_to() to send(), which now accepts an options object only)
Add OutboundHelper to InteractionMachine
Add a default for 'endpoints' in IMConfig
Add docs for OutboundHelper
Document delivery classes in ContactStore.get
Docstring fixes and improvements for OutboundHelper.send()
Use 'twitter_endpoint' instead of 'endpoint' in OutboundHelper.send() test
Merge branch 'feature/issue-105-add-outbound-resource-helper' into develop