Completed TODO in tensor.py:as_tensor_variable which said to use the Apply default output mechanism.
Added tests to excited the various possible failure scenarios.
Incorporated review comments.
Merge branch 'master' of https://github.com/Theano/Theano into mastery

Conflicts:
	theano/tensor/tests/test_basic.py
Streamlined test.
Merge pull request #2086 from daemonmaker/todo_astensorvariable_applydefaultoutput

Completed TODO in tensor.py:as_tensor_variable which said to use the App...