Generation no longer bails when no post-processor defined

Currently if there is no mapping for the input file extension in the undocumented `options.processors` object, the generation process bails with an unhelpful 'invalid extension' message.

This object contains functions to be applied to the results of the template engine on a per-extension basis. Rather than aborting generation due to an unrecognized extension, it makes more sense to carry on with the template results verbatim.