Gulp file cannot be parsed when mocha is used (and a temporary workaround)

[akfish]

This is a wired bug. Whenever mocha is used in the gulp file, it will not be parsed correctly thus the tasks cannot be listed.
Basically it's because atom's Task environment has document object but no location. This confuses mocha (See also mochajs/mocha#1654)

A temporary workaround is to expose a fake location object to global in your gulpfile:

GLOBAL.location =
  href: process.cwd() + "/"

A pretty corner case here, so not sure when and who will decide to fix it in which project. Just documented it here in case some one has the same problem.