add DS_Store to gitignore
Update dot op to support n-dimensional variables (numpy semantics)

-call numpy.dot for inputs with dim == 0 or dim > 2
-add gradient calcs for various cases
-add infer_shape for various cases
-update docstring
re-enabled tests of tensor dot products (using dot op)
add tests for int inputs (perform)
This test had the same name as the previous one and wasn't run
removed corner case, wrote grad for tensors more clearly, added more comments
added docstring and examples for tensordot
unit tests for infer_shape: all combinations of scalar/vector/matrix/tensor3 dot products
updated comment to match code
reversed tensordot arguments to remove transpose for xgrad. updated comments.

ygrad still requires a transpose.
removed integer tests -- weren't doing anything real
expanded tensordot docstring to explain default axes argument
# followed by """ sometimes messes up syntax highlighting

the closing """ is ignored because of the #
replaced TensorDot and TensorDotGrad Ops with a function
update unit tests to use new tensordot function, remove infer_shape tests for tensordot and tensordotgrad
removed GPU-specific tensordot and optimization; no longer needed.
create dot function to call the new tensordot function for inputs with more than 2 dimensions
check for vector inputs to tensordot (can't have negative axes)
check for non-variable inputs to tensordot
improve error checking for axis arguments

1. make sure they are tuples
2. was checking if the max axis was > available dim, should have been
>= available dim