Use Extlib::Inflections.camelize to convert the adapter name into a c…

…lass name

* Extlib::Inflections.classify singularizes the adaper name, which can
  incorrectly strip a trailing "s" from the adapter name, eg: redis => Redi

[#890 state:resolved]

lib/dm-core.rb

@@ -176,7 +176,7 @@ def self.setup(*args)
       options = normalize_options(uri_or_options)
 
       adapter_name = options[:adapter]
-      class_name   = (Extlib::Inflection.classify(adapter_name) + 'Adapter').to_sym
+      class_name   = (Extlib::Inflection.camelize(adapter_name) + 'Adapter').to_sym
 
       unless Adapters.const_defined?(class_name)
         lib_name = "#{adapter_name}_adapter"