Updated package.json
Bump version.
Merge branch '0.9.x' of https://github.com/michael/data into 0.9.x
updated packages.json
Allow to add versioning after construction.
Some comments.
Only one event for property updates done via update and set.
Fix test.
Updated package.json
Use general way to invoke Operation apply.
Graph.addIndex now reuses an existing index instead of throwing an error.
Helper function for defining properties.

Currently this is redundant with Node.defineProperties.
For Collection I wanted to use the same... maybe we should
turn it into a Node.
More explicit error when providing null/undefined to graph.get().

plus: dropped an unused API option that allows 'graph.get()'
with the path given as multiple strings instead of an array.
Early fail in certain cases when property path is invalid.
Fix regression.
A getter for indexes.
Fix deserialization of graph operations.
Updated package.json
Adapt tests after changes in Test API.
Clone arrays in Graph.set