static reply app + test
Switch static_reply tests to new helpers.
using dynamic config (thanks @jerith)
Merge branch 'feature/issue-650-static-reply-app' of github.com:praekelt/vumi into feature/issue-650-static-reply-app

Conflicts:
	vumi/demos/tests/test_static_reply.py
making reply_text required (thanks @hodgestar)
better demo
using default get_config() so it can possible be used in Go
Merge branch 'feature/issue-650-static-reply-app' into develop