* added mse_loss, nll_loss and kl_div_loss
* fixed axis not defined error in nll_loss
* fixed axis not defined in kl_div_loss
* added tests for mse, nll and kl_div
* modified docstrings and added reduce helper func
* updated docstring in kl_div_loss and moved helper func
* added new kl divergence implementation
* added reduction to test
* updated docstring of kl_div_loss with correct spelling
* added losses to nn.rst in docs
* MLE and L1 loss functions
* logsoftmax change and tests
* subtract max logit for numerical stability
* l1 name change
* cross entropy reduction + unit tests
* docstrings
* l1 test name change
* old loss impl + default none
* style
* MLE and L1 loss functions
* logsoftmax change and tests
* subtract max logit for numerical stability
* l1 name change
* cross entropy reduction + unit tests
* docstrings
* l1 test name change
* old loss impl + default none
- The exponent and base were swapped because accelerate is using
exponent-base instead of base-exponent
- Fix also the test for binary ops as it was testing op(x, x) which
couldn't catch ordering errors like that
