Fixed adapter class lookup for default sqlite database.yml

The official rails templates changed the adapter
name to 'sqlite' in the created database.yml file.
We need to account for that in dm-rails and we
agreed upon calling it sqlite in DM land anyway.

lib/dm-rails/storage.rb

@@ -47,7 +47,7 @@ def with_local_repositories
         end
 
         def lookup_class(adapter)
-          klass_name = adapter.camelize.to_sym
+          klass_name = normalized_adapter_name(adapter).camelize.to_sym
 
           unless Storage.const_defined?(klass_name)
             raise "Adapter #{adapter} not supported (#{klass_name.inspect})"
@@ -56,6 +56,10 @@ def lookup_class(adapter)
           const_get(klass_name)
         end
 
+        def normalized_adapter_name(adapter_name)
+          adapter_name.to_s == 'sqlite3' ? 'sqlite' : adapter_name
+        end
+
       end
 
       def initialize(name, config)
@@ -88,7 +92,7 @@ def charset
         @charset ||= config['charset'] || ENV['CHARSET'] || 'utf8'
       end
 
-      class Sqlite3 < Storage
+      class Sqlite < Storage
         def _create
           return if in_memory?
           ::DataMapper.setup(name, config.merge('database' => path))