Using secure version of rubygems to get rid of warning message.
Updated tests and code to support partial override of default configuration paramters.
Updated spec tests so that some failing travis tests will be excluded from the travis run.  Removed 1.8.7 from travis since it has never passed.
Added support for on_loaded callback to StandaloneMigrations plus tests for the callback functionality.
Merge pull request #100 from ejhayes/master

Allow .standalone_migrations to override partial configuration