added a fix for no-cache content

the real fix is to use NetworkAccessManagerSlim
the other thing is just the partial solution, which
has its own bug

So to run the basic example with this fix you have to set
the NetworkAccessManager:

from ghost import Ghost, NetworkAccessManagerSlim
ghost = Ghost(network_access_manager_class=NetworkAccessManagerSlim)
page, extra_resources = ghost.open("http://jeanphi.fr")
assert page.http_status==200 and 'jeanphix' in ghost.content

although this example had no bug in the first place :D
A real example can be seen in tests/noCacheTest.py
There is also documented where the shortcomming of the partial
solution is.