Make it optional to specify the `.jsx` (and `.coffee`) extension

[pscanf]

As the title says. Would it be doable at all or are there technical issues that prevent it?

[zordius]

We already provide option for this. The default transpiler option is only transpile .jsx files by babel and only handle .coffee files with coffee. And you can pass different regexp into options.transpile.babel.include or options.transpile.coffee.include to customize it. Please refer to README.md for more document, thanks.