Compose with EllisEndpoint rather than inheriting from it
Refactor to enforce a cleaner separation between provisioning a line in Ellis and making calls
Fix up SIPp tests
Refactor test skipping to be composable
Merge remote-tracking branch 'origin/master' into ellis_refactoring
Update skipping of SUBSCRIBE test
MockAS is unused; remove it
Move SIPp code into a separate file to reduce clutter
Code review feedback
Merge remote-tracking branch 'origin/master' into ellis_refactoring

Conflicts:
	lib/tests/subscribe.rb
Merge pull request #64 from Metaswitch/ellis_refactoring

[Reviewer: Alex] Ellis refactoring