Build with Node, part 2: deprecate Makefile and remove configure.py

This change removes `make` and the associated `configure.py` script from the
workflow.  Instead, consumers of the package should use distribution release
files from a git tag, zip download, npm/Bower install, or a CDN.  Those wishing
to build from source should use the npm scripts as shortcuts.  (Anyone doing
active development will likely want to install Ninja globally to save some
typing.)

Closes #7.