call to it caused infinite loop in global build

In the global build, the it function contained a reference to
itself. Instead capture reference to the original it for calling.
Merge pull request #2 from cowboyd/rename-reference-to-original-it

call to it caused infinite loop in global build
allow `it`, `xit`, `it.skip` and `it.only` forms.

Mocha allows calling `it()` with only a test title, which is the syntax
it uses for marking a spec as pending. `xit` delegates to `it` and does
not pass along any callback. It also supports using `it.skip()` to mark
a particular test as pending.

Another modifier for tests is `it.only()` which causes the test runner
to only run that single test for the next run.
fix jshint errors
Merge pull request #4 from cowboyd/it-only-and-it-skip

allow `it`, `xit`, `it.skip` and `it.only` forms.