Testing Module for Simple Graph Operations Added.

All the Operations are not included
Complement function for Undirected Graphs added
Compose Function for undirected simple graph added

Previously written composite function judiciously modified.
Previously defined Complement function modified.
intersection,difference and symm. difference added

name of compose operation changed to union
exception class of staticgraph added
set diff used in the operations for fast execution

testing module of graph operations altered to include testing of failures.
BFS traversal of undirected graphs added
DFS traversal for undirected simple graphs added

exception class for absence of a specific node in the graph added,
used during traversal for checking presence of source node.
minor error corrected.
Tracking Predecessor nodes for traversals added.

Two dimensional numpy array returned, 1 for the nodes reached, another for the predecessors
Minor error in traversal module corrected.
Sngl src shortest path for unweighted graphs added

Implemented only for undirected graphs.
Test module for operatns on simple digraphs added.
Module for simple digraph operations added.

Unary and Binary operations included.
traversal.py module changed to graph_traversal.py

Only traversal algorithms for simple undirected graphs is in this module.
useless mem  allocation removed in graph_traversal

previously arrays were uselessly allocated with larger memory spaces.
Module implementing digraph traversals added.
Traversal modules modified to return smaller array

Earlier space was allocated even for the vertices not traversed at all.
Docstrings of functions made more informative.

modified for traversal and shortest_path functions.
Floyd's algo for unweighted & undirected graphs.

Floyd_Warshall's algorithm used to find all pair shortest paths