Shape + selection tool

[blobotic]

Add a tool to the toolbar that lets the user add in a variety of default shapes. This requires a selection tool to go along with it so that these shapes are movable after the fact (canvas.selection = true/false from FabricJS).

The user should be able to customize all options available by default via Fabric.

This extends the functionality of #12.

[blobotic]

c51c634

added selection tool