Rename CrossentropyLoss to CrossEntropyLoss

[juliohm]

Can we follow the camel case convention like with the rest of the loss names? I can submit a PR with a deprecation warning if it is ok.

[joshday]

Sounds good to me!

[juliohm]

Thank you @joshday will submit another PR today for this. Meanwhile, I appreciate if you can take a look at #122.