build: Implement Grunt workflow (via npm test)

Slims down the already-merged (!) VE gruntfile, removing jsduck and
build task.

To test, `npm test`.  This runs jshint, csslint, and banana.
Not jscs yet, run `grunt jscs` to see what needs fixing (fixes are in the
TOC patch stack, see gerrit I2400db13).

TODO: should we convert some or all of pre-commit script to this and
transition from Makefile?

Change-Id: Ib552c76f685d3f34d37bed297953f98fddf4bb9d
Merge "build: Implement Grunt workflow (via npm test)"