Renamed TriangleRenderer to Renderer2dStrip.

Going to prepend renderer types with Renderer in future, so they
cluster together when typing or looking at files.
Renderer cleanup and consistency.

2d renderers inherit from Renderer2d, which makes the renderable
objects compatible across various renderers (though we may need
to pass a hint for vertex arrangement).
Updated RendererTest to test both VBO and non-vbo versions of a
2d batch renderer. By far the most expensive part is gathering up
the transformed vertices.
Renamed Renderer2d file.
Added message passing system from Word Shift.
Added license to header files in message system.
Comments in Messenger and Receiver.
Spacebar only to cycle the renderers.
Cleaning up and standardizing the expanded line functions.
Changed expanded path skeleton representation.

Makes sliding the path along the screen much simpler.
Renamed to shiftFront() and shiftBack().

Better explains what happens.
Added erase_if templated method to collection utilities.

More flexible than vector_erase_if; need to give it some time to
see if it's actually better.
Using a dirty flag on expanded paths.

Since they are long and building the outline can be expensive, we
just check whether updates are needed on draw and then perform them
at most once per frame.
Starting on a Scene2d sample (and building out that api).
Fullscreen renderer test app.
Updating renderer and locus to enable more const behavior.
Updated to match randomization setup of PupTent sample.
Updating README with thoughts about the future of Pockets.

Going to make it much leaner soon.
Center the registration point.
Moving lots of stuff into new blob/ folder.

Naming is to suggest that these things aren't necessarily
useful. Many are, but I'm not going to be supporting them as
I move forward.

Functionality either is or will be duplicated/improved upon in
PupTent, which is a bit more opinionated about how it is used
and therefore more generous in the returns it give to users.
The entity system that it's built around is allowing me to think
about each piece in a way that is closer to my ideal. This is
especially apparent in the case of the Locus and the relationship
of geometry expansion tools to the renderer(s).
ConnectionManager for maintaining a list of connections.