Convert HTTP API vumi worker to new-style config and add concurrency_limit option.
Merge branch 'feature/issue-433-configurable-concurrent-clients-for-http-api' into develop
Merge branch 'develop' into develop-frontend
Add forgotten dummy dialogue state
Merge branch 'develop-frontend' of github.com:praekelt/vumi-go into develop-frontend
Merge branch 'develop-frontend' into feature/issue-438-end-dialogue-state