Check keyword arguments passed to Reader constructor. Throw an AssertionError
if an invalid argument is passed.

Before this change, specifying an invalid keyword argument would cause the AsyncConn
to fail quietly in the Tornado default exception handler during run-time.

Remove trailing whitespace

Check keyword arguments in Writer constructor and add unit test
Merge pull request #87 from stanhu/verify-reader-kwargs

Check keyword arguments passed to Reader constructor. Throw an Assertion...