Add a migration to load all iTree regions

Deb gave the ok to include these in repository. The data in this
migration was generated from an updated region shape file from which the
lakes have been removed.
Merge branch 'master' of github.com:azavea/OTM2 into topic/add-all-itree-regions
Merge pull request #834 from jwalgran/topic/add-all-itree-regions

Add a migration to load all iTree regions