Revert "Made it raise NotImplemented if you don't return something valid from a controller action, as requested in lighthouse ticket #1201."
Revert "Made it raise NotImplemented if you don't return something valid from a controller action, as requested in lighthouse ticket #1201."

This reverts commit 7732e6355e8dd730caeea798d23dd7fb98898d37.

merb/merb-core,merb/merb-core