Snap library functionalities

Snap Wrapper
DegreeCentrality, CommunityDetection, CommunityEvolution
UGraph:
addNode, addEdge, delNode, delEdge, isNode, isEdge, nodeCount, edgeCount, getNode, getFirstNode, getLastNode, dump
Node:
getId, getDeg, getInDeg, getOutDeg, getNbrNId, getNext, getPrev

Added example
js implementation of evolution detection - evolutionJs
visualization of evolution - drawCommunityEvolution