test that CoffeeScript can set global vars using this
Remove unneeded code to pass "this" to top-level code.

Reverts commit c1f2379710e8d44a806c9e17583f0d6bb2b609d6, as @glasser
discovered it isn't needed and so is an unnecessary complication.

Add a space after the leading "(function(){", to make generated code
easier to read.
add documentation for setting global vars in CoffeeScript
Wrap new doc section, link to `global` in the Node API, and mention @.
Merge branch 'pr/869' into devel