Fix source map issue

I fixed source map issue of coffee-mode.

Wrong source map files is generated when compile commands
(such as coffee-compile-file) are executed, if you specified
source map option(-m) to 'coffee-args-compile'.

Please upgrade coffee-mode version if you add source map
option to compile options. You can upgrade it from MELPA.


Please report us via github issues if you have any problems
or suggestion.