Tutorial for C op

Work in progress.

This is the first version of the tutorial on extending theano with C ops. I'm looking for feedback from people with experience with it to help check for factual errors as well as from people with little experience extending theano to ensure that the concepts are explained clearly enough for new contributors to Theano. Thanks.
I find this part not clear: " by any anyone". Maybe it is good, just not in what knowledge of English. I would tell something like:
it means it is not used by anyone anymore and ...