Add 'not null' constraint and index to reply token
Remove FillInReplyTokensTransition

Removing this because we now have a not null constraint. It is
impossible to test this transition.
Merge pull request #91 from codecation/add-reply-token-constraints

Add db constraints to reply token
Merge branch 'add-reply-token'

* add-reply-token:
  Remove FillInReplyTokensTransition
  Add 'not null' constraint and index to reply token