Better management of multiple arguments in shebang lines.

Fixes quicksilver/quicksilver#1274
Don't read the complete file in memory.
Module => Plugin.
Use UTIlity methods.
Use UTIs to tell script files.

It still won't work for files without extensions but now there's no need for an 'extension' list.
Memory leak.
File descriptor leak.
Merge pull request #9 from quicksilver/fix_1274

Better management of multiple arguments in shebang lines.