Allow a block of default content with cms_snippet_content.

If such a block is given, first an attempt is made
to find a matching Cms::Snippet, if one is found its content is
displayed (current behavior unchanged).  If no Cms::Snippet is found,
a new one is created using the content captured from the block.
Merge branch 'master' of git://github.com/greenriver/comfortable-mexican-sofa into greenriver-master

Conflicts:
	lib/comfortable_mexican_sofa/view_methods.rb
	test/models/view_methods_test.rb