Saving a modules __dict__ attribute

Possibly a follow up for #35, but saving a session doesn't save the state of the modules:
```pycon
Python 3.4.1 (default, May 19 2014, 17:23:49) 
[GCC 4.9.0 20140507 (prerelease)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> import test
>>> test.a = 2
>>> dill.dump_session()
>>> 
==========================Restart==========================
Python 3.4.1 (default, May 19 2014, 17:23:49) 
[GCC 4.9.0 20140507 (prerelease)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> dill.load_session()
>>> test
<module 'test' from 'test.py'>
>>> test.a
1
>>>
```
test.py:
```py3
def f():
    print(x)
a = 1
```
I think this code does the job, but it may need a few adjustments, depending which modules need to be pickled.