add Tri op, tri/tril/triu functions
add triangle tests
add Nonzero Op, function, tensor method
add nonzero test
move Nonzero docstring from the function to the class
add 1D test for nonzero
add flatnonzero and tests
add nonzero_values and test, also update nonzero docstring to reflect new indexing behavior
change Op to return matrix; change function to return either tuple or matrix
fix typo in docstring
missing if/else for return_matrix
guarantee zeros in tests
avoid vstack of 0-length arrays; cast result as int
make sure numpy.nonzero returns tuples with length > 0 before numpy.vstack
raise error for scalar values
move tests into class
bump to start testing process again
Merge pull request #1181 from jlowin/triangle

Add triangle/nonzero functions