[#64349062] Pickle and unpickling for GraphCollection objects

1. It works fine for Pickling and Unpickling GraphCollection Objects
and other general graph objects as well
2. Tested the errors and exceptions as well
Merge branch 'ramki' into python
Merge branch 'python' into erick

Conflicts:
	.DS_Store
	tethne/networks/papers.py
resolved conflict