[WIP] Total efficiency calculation

I added two methods to the Efficiency class to compute the total efficiency (weighted by the bin contents of the total histogram). I also implemented the error computation (uncorelated accross bins).

Quentin
I ran make trailing-spaces and it fixed a bunch of files (see list below). I also ran make pep8 and fixed the errors in hist.py.  I also removed the else statement and the parenthesis as you suggested.

rootpy/extern/close_variable.py
rootpy/extern/decorator.py
rootpy/extern/lockfile/pidlockfile.py
rootpy/extern/lockfile/sqlitelockfile.py