Add function and method definition syntax elements.

This adds coffeeFunction and coffeeMethod syntax elements which are linked to
coffeeStatement and coffeeObjAssign, respectively. This ensures that existing
themes will continue to behave as they have, but make it possible to highlight
functions and methods separately ala Sublime Text.
Fix all but a few edge cases.
highlight functions
Merge branch 'master' of github.com:zeekay/vim-coffee-script