Refactor getTeams method & unit test to fix test suite

[compumike08]

I refactored the getTeams method in Organization.js to use the new _request method instead of the deprecated _requestAllPages method, and I refactored the associated unit test to use assetSuccessful and done(), instead of returning the output from a chained .then handler method.

After making these changes, two of the three unit tests which were failing are now passing. The one unit test which is still failing is not actually a problem with the unit tests themselves, but rather is being caused by the test harnesses inability to properly authenticate to GitHub.

@clayreimann @mtscout6 @AurelioDeRosa @alexcanessa