Accepts CoffeeScript requires with spaces. Fixes #57.

Updated RequireReference regex to match either an opening parenthesis or
space after the "require" keyword, and made the closing parenthesis
optional. These changes allows valid CoffeeScript syntax to be accepted.
Merge pull request #58 from amageed/57-accept-coffeescript-require

Accepts CoffeeScript requires with spaces. Fixes #57.