Add ruby_executable_hooks to hashbang recognition

Adds the name of another executable to the grammar's hashbang-recognition pattern.

The executables generated by RubyGems use this as their first line:

    #!/usr/bin/env ruby_executable_hooks

Since the files have no extension, there's nothing to activate the grammar.

Syntaxes/Ruby.plist

@@ -79,7 +79,7 @@
 	<string>(?x)
 # Hashbang
 ^\#!.*(?:\s|\/)
-(?:ruby[\.\d]*|macruby|rake|jruby|rbx)
+(?:ruby[\.\d]*|macruby|rake|jruby|rbx|ruby_executable_hooks)
 (?:$|\s)
 |
 # Modeline