It is expected that support for promises will be available in whatever
environment liza is run. Here, we're adding a shim for the sake of testing
in ancient environments.
It's almost as if I'm stuck using an ancient environment somewhere...*cough*
``Building'' Liza will not be required to use it; see ease.js for the style
of building that will be used here. In particular: the build process will be
used for minification and the creation of distribution archives, but one can
simply include the source files (using, say, node.js) to use it without
building.