Mixed

no news
- better error message
- tests use floatX
- fix to error detection in new stuff
- doc
- pep8
- faster tests
- speed up perform of op with c code.

news.txt
- add theano.tensor.extra_ops.to_one_hot
- fix crash when alloc zeros of more then 2G: (Frederic B., reported by Alessandro Sordoni)
Ok then.