Initial work on Lotus::Model.adapter
Replace Lotus::Model::Adapter with Lotus::Model::Config::Adapter
Add test for Lotus::Model.adapters
Remove #default attribute from Config::Adapter

Instead, set it to Model.adapters[:default]
Initial work on Lotus::Model::Configuration
Merge pull request #41 from joneslee85/issue-33

[WIP] Allow Lotus::Model to register adapter instance