Added graph functions Added graph functions
Fix : Forgot a term on the zeros matrix
Enhanced gradients and not working divs
Divs are done --> need to be tested
Added docstring
Fix brackets
add of the doc, preperation of the grad and div to get the *arg
changed some mistakes in the grad weights
fix gradients for more accepted input matrix size, added tv_norm methods
TODO test both grads and tv norm
Typo fixed in _norm_tv4d()
Modified norm tv according to the new grads
Merge branch 'grad' of github.com:epfl-lts2/pyunlocbox into grad
New version of grad, div with wights (in branch poids).  norm_tv one the way
fix typo and pep8
Merge branch 'poids' into grad

Conflicts:
	pyunlocbox/functions.py
Doc orthographic corrections
Lite modifs on grad and div functions, some exceptions added and some comments modifications
adding norm_tv weights options, correcting some problems in divergence weights
Merge branch 'grad' of https://github.com/epfl-lts2/pyunlocbox into grad

Conflicts:
	pyunlocbox/functions.py
Added 2d prox TODO test