Remove deprecated pydot drawing functions.
Add get_fobj() to networkx.utils
Better pydot conversion. Add draw_pydot().
Small typo. Missing pydot import. Updated tests.
Fixing default show mode for draw_pydot.
Add documentation for inline pydot drawing within IPython notebooks.
Adding draw_pydot to reference documentation.
Whitespace changes and removing the usage of @requires
Add nxParams, a dict-like configuration for parameters.
Make draw_pydot() use nxParams['pydot_show'] when show=None.
Update documentation for globally changing display mode.
Updating docstring for draw_pydot().
Merge branch 'pydot' into pydot2
Incorporating changes introduced in #905.

Conflicts:
	networkx/drawing/nx_pydot.py
iteritems -> items for Python3 compatibility.
Added tree recognition functionality
Removed the useless self_loop check and improved formatting
The is_tree() function has been correpted to check the "directness" of the input graph
with the appropriate is_directed() function.

With this change, graph of the class MultiGraph can be correctly recognised as tree too.
The test suite has been modified accordingly
Added forest recognition functionality and added tests for it.
Slightly modified the is_tree() function.
added documentation for return type to `draw_networkx_nodes`,
`draw_networkx_edges`, `draw_networkx_labels`, `draw_networkx_edge_labels`.
pep8 compliance work