Check for a cluster in ContextTestCase.
Split off ClientTestCase from ContextTestCase.
Remove a line of whitespace.
Have TestCountRoundTrips be a ClientTestCase.
Have TestContextCreation be a ClientTestCase.
Make TestKeyAndPushArgs a ContextTestCase.
Make TestDecoratorBase a ClientTestCase.
Make TestVectorizeDecorator a ContextTextCase.
Make it work on Python 2 and Python 3.
Remove unused import.
Tweak skip message.
Fix PEP8 nit.
Merge pull request #511 from enthought/feature/skip-tests-without-cluster

Skip tests that need an ipcluster if one isn't available