Calling callback in kml tests

Also reordering things so we have `expect(got).to.xmleql(expected)`.
Calling callback in GML v2 tests
Calling callback in GML v3 tests
Calling callback in WMS capabilities tests
Get rid of unnecessary `waitsFor` function

This was a relic from the Jasmine tests.  Mocha tests have a built-in timeout.  Async tests are registered with a function that takes a callback.
Merge pull request #810 from tschaub/async-tests

Proper async testing