Add support for Cool

This change includes a brief (non-sensical) sample program I wrote to
illustrate many of Cool's language constructs, as well as a simple rule
to distinguish Cool files from Common Lisp or OpenCL (it has a line that
starts with the word 'class'). Further, it includes a second example
program adapted from an example contained in the Cool distribution
(list.cl), which contains a few further language constructs and captures
the style of a Cool program.
Merge branch 'master' into cool

Conflicts:
	lib/linguist/heuristics.rb
	lib/linguist/languages.yml
	lib/linguist/samples.json
Be explicit about tm_scope
Adding Cool grammar
Merge pull request #1796 from github/cool

Cool