Defaulted all ORMs that used the mysql gem to use mysql2 when the
options mysql and mysql2 are used and to force the mysql gem only when
mysql-gem is specified in the generator.
Merge pull request #1107 from padrino/default-to-mysql2

ORMs use mysql2 instead of mysql
Reverted mongoid generator for to use config/database.rb instead of
config/database.yml.

However, I left the indications on how to use that on the generated
config/database.rb.

Also implemented ENV['MONGO_URI'] as @j15e's suggested. It will default
to it if set.
Merge pull request #1108 from padrino/revert-mongoid-to-use-database-rb

Reverted mongoid generator to use config/database.rb instead of yml file.
Merge remote-tracking branch 'upstream/master' into super-admin