Assert that stream is auto-closed in AboutTryWithResources

[DavidWhitlock]

Based on the discussion in #42, I suggest that we add an assertion that verifies that the close method of the InputStream is invoked in the "try with resources" try block in the AboutTryWithResources. lookMaNoClose() koan.

Unfortunately, there is no isClosed method on InputStream. @matyb suggests that the koan have a helper method that attempts to read from the closed InputStream to verify that it is closed.

See also http://stackoverflow.com/questions/8655901/how-to-check-whether-an-outputstream-is-closed