Removing Resource, DataStore, and Client modules

- classes defined under Resource module now defined under Stormpath module (the same goes for classes defined under DataStore and Client)

- Stormpath::DataStore::DataStore (class) now resides under Stormpath module

- Stormpath::Client::Client (class) now resides under Stormpath module

- Stormpath::Resource::Utils --> Stormpath::ResourceUtils (Resource module has been removed)

- Stormpath::Resource::Error --> Stormpath::ErrorResource (Resource module has been removed)
Updating rdoc to reflect new class structure