Allow deploys for projects using sql schema_format.

For a rails project using database-specific constraints, the file
describing the state of the database is db/structure.sql instead of
db/schema.rb. This allows the existing tasks to use either file when
creating or migrating a database.

see http://guides.rubyonrails.org/migrations.html#schema-dumping-and-you
Merge pull request #90 from PaulOstazeski/1.x

Allow deploys for projects using sql schema_format.