Updated specs to pass with all adapters, even the Yaml adapter
Updated specs to pass with all adapters, even the Yaml adapter

* Updated to not monkey patch Symbol with operators by default
* Stopped monkey-patching Module with #chainable and #extendable, are
  now mixed-in as needed from DataMapper::Chainable
* Removed some dead code paths
* Reformatted and rearranged code to help with coverage testing
* Added AbstractAdapter.normalize_options and refactored AbstractAdapter
  to use it as well as DataMapper.setup
* Moved exception definitions into lib/dm-core.rb

datamapper/dm-mysql-adapter