Only parse js extensions

[jwalton]

For require and falafel transforms, it would be nice if there was an option to only parse js type files by default. Trying to run a JSON file through a require or falafel transform wouldn't go vey well, for example.

• ".js"
• ".coffee", ".coffee.md", ".litcoffee" - via coffeeify
• "._js", "._coffee" - Streamline.js
• ".jade" - jadeify
• ".vash" - vashify
• No ".hbs" from hbsfy, because Handlebars can't inline Javascript code?

It would be nice if there was a way for end-users to specify what extensions should be processed in the module config, or even for them to specify exactly which files should be processed for performance optimization.

[jwalton]

Fixed via 010023c.