Build script verifies that installed version of node.js is supported.

+ Node APIs change with some frequency.  Sometimes errors occur whose symptoms don't obviously point back to the platform version.
+ included procstreams because jake's process API is a bit klunky.
Going with a far far simplier way to check the node.js version.

+ for now, we're going to do exact matches since node.js changes frequently.
Elaborated some of the next User Stories
(spike) serving up a static file

+ sketch of how virtual paths map to physical paths
+ an attempt at proper error reporting (e.g. 404, 500).
Now server is serving up static files.
Moved all source code under the "src" directory.  "build" is now for build output.

+ I wanted a place to put some files generated by tests, but having seen other kinds of generated artifacts come out of other systems, I'll do something cheap, easy, and conceptually flexible: all source files are under "src" and any generated files (for any reason) are under "build".
Build script ensures "build" directory exists.
Relative filesystem paths are now canonical. Callbacks to server are properly passed through.
Build script can create and purge the build directory.

+ by default, the build will purge the build directory
Tests/Specs now put their generated files in a separate directory under "build".