Tweak test formatting; fix order-dependent failure

The order-dependent failure has been been commented in code.

After manually bisecting the test suite, I was able to determine that
the template cascade tests were leaving the `@@template_priority_path`
set to an overridden value in tests run afterward.

lib/gollum/views/template_cascade.rb

@@ -11,9 +11,13 @@ module Precious
       end
 
       def first_path_available(name)
-        priority = File.join(template_priority_path, "#{name}.#{template_extension}")
         default = File.join(template_path, "#{name}.#{template_extension}")
-        File.exists?(priority) ? priority : default
+        priority =
+          if template_priority_path
+            File.join(template_priority_path, "#{name}.#{template_extension}")
+          end
+
+        priority && File.exists?(priority) ? priority : default
       end
 
       # Method should track lib/mustache/settings.rb from Mustache project.