Remove $schema line from Builder schema

The $schema line was causing json-schema to fail validation. That line
doesn't have all that much useful information anyway.
Unify ShapeData schemas

Use union notation in JSON schemas to unify the circle and rectangle
schemas into one file.
Add JSON frontend schema file

Add schema for use in a web frontend.
Add simple JSON verification script
Move JSON validator to its own subproject

It has dependencies distinct from those of node-markup, so move it to
its own folder so I can have a custom install script in there.
Add tutorial file describing how to use JSON

Explain specification and include example strings for JSON and Markup
strings in frontend and backend scenarios.
Improve wording of circle draw instruction

The original wording didn't make much sense in the TUTORIAL.md
documentation.
Merge branch 'documentation'
Point script to right binary location

Our node is at /usr/local/bin/node.
Have run script use current enironment

Do not clear the environment variables before trying to run Node.
This frees up the server admin to put binaries wherever needed. At this
point, Node must be in $PATH.
Change node-markup.sh shell to bash

/bin/sh can have different results on different machines. /bin/bash
does exactly what is necessary.
Pin working jsdom dependency.

It turns out that a change[0] between jsdom 0.5.6 and 0.5.7 just broke
node-canvas.  Entirely.  And the maintainer didn't release another 0.5.x
to fix it. >_<

This took a long time to track down, so let's save everyone (including
ourselves) the trouble.  Pin a more specific version, since we now have
no confidence in jsdom's version numbers.

[0]: https://github.com/tmpvar/jsdom/commit/6ed9c6bc0d882c034e8710dc23e6d01e35f52255
Merge branch 'pin-working-jsdom-dependency'
Merge branch 'new-binary-location'