Update README.md
Removed adding the conveyancer if it does not exist. The conveyancer is adding in the fixtures when adding one
Merge pull request #4 from LandRegistry/remove-add-conveyancer

Removed adding the conveyancer if it does not exist.
Make these cols nullable for now, then drop them if really not needed
Change code to token
Merge branch 'master' of github.com:landregistry/introductions
Merge branch 'master' into add_tests

Conflicts:
	introductions/server.py