[Project] Transform config names to snake case for define

lib/cocoapods/project.rb

 require 'xcodeproj'
+require 'active_support/core_ext/string/inflections'
 
 module Pod
   # The Pods project.
@@ -260,7 +261,7 @@ module Pod
     # @return [String] The preprocessor definition to set for the configuration.
     #
     def define_for_build_configuration(name)
-      "POD_CONFIGURATION_#{name}".gsub(/[^a-zA-Z0-9_]/, '_').upcase
+      "POD_CONFIGURATION_#{name.underscore}".gsub(/[^a-zA-Z0-9_]/, '_').upcase
     end
 
     private

spec/unit/project_spec.rb

@@ -417,6 +417,14 @@ module Pod
             ['POD_CONFIGURATION_MY_AWESOME_CONFIGURATION=1', "$(inherited)"]
         end
 
+        it 'transforms camel-cased configuration names to snake case' do
+          configuration = @project.add_build_configuration(
+            'MyAwesomeConfiguration', :release)
+          settings = configuration.build_settings
+          settings['GCC_PREPROCESSOR_DEFINITIONS'].should ==
+            ['POD_CONFIGURATION_MY_AWESOME_CONFIGURATION=1', "$(inherited)"]
+        end
+
         it 'adds DEBUG for configurations based upon :debug' do
           configuration = @project.add_build_configuration(
             'Config', :debug)