Heap is modified to work only with graph nodes
add transition properties
initial support for transition animations specified in style; mostly works but kind of buggy
fix transition from transition
fix transitions being triggered on init stylesheet apply
constant transitions working but initial state transition not right direction
Dijkstra algorithm implementation using minheap
merging for dijstra heap pull request into 2.2
https://github.com/cytoscape/cytoscape.js/pull/435

Merge remote-tracking branch 'refs/remotes/ikavalio/2.2.0' into 2.2.0

Conflicts:
	debug/init.js
	src/style-apply.js