Updated InMemoryAdapter and YamlAdapter
Updated InMemoryAdapter and YamlAdapter

* Updated InMemoryAdapter so internal representation of resources are
  Hashes instead of Resource instances.
* Updated InMemoryAdapter#update and YamlAdapter#update to pre-calculate
  the attributes Hash, and then use Hash#update to change each record
  rather than iterating over each field within the loop.
* Updated YamlAdapter to use Model#storage_name to get the yaml file
  name.  This allows configuring of the filename via the Model if the
  user wishes.
*

* Misc minor code tweaks to use coding conventions within dm-core

datamapper/dm-yaml-adapter,lgierth/dm-yaml-adapter