Update Clojure interop to support new OnSubscribeFunc with rx/fn.
Remove unnecessary Observable constructor

- fixed unit tests that relied on it
Merge pull request #345 from benjchristensen/unit-test-cleanup-with-create

Remove unnecessary Observable constructor
Merge pull request #344 from daveray/covariant-support-clj

Update Clojure interop to support new OnSubscribeFunc with rx/fn.