Fix PersistentNdarrayLoad problem restoring same object multiple times

Update elemwise_openmp_speedup.py

Added cuDNN v5 support & Added optional dependencies to setup.py

Removed duplicate print code for "Fast op".

Check RST files in '/theano/doc/' to follow numpy's docstring + Fix elemwise

fix gh-4328 This was done for python3, but not python2.

Moved theano.sandbox.softsign to tensor/nnet/nnet.py. Added test. #4314

Add broadcastable dimensions in opt where needed

- Move the contribution requirements on top, so that contributors read
them even if they know how to setup GitHub
- Fix minor errors
- Remove commented code in elemwise