Generator tests are never run

[balderdash]

AFAICT, we were never able to run the tests under tests/generators/ from the command line. In upstream blockly, the tests are run by opening up tests/generators/index.html in Firefox/Safari (security restrictions prevent them from working in Chrome) and clicking a button.

That page has been completely broken since my compilation changes in #135, but it was mostly broken ever since we spun out the separate blockly repo (it throws javascript errors attempting to load blocks, before even trying to run the tests).