Update task.js - a plugin can be a collection and a task at the same tim...

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I am building a common build system for several frontend-projects and therefore am creating a super-task - a task composed of other tasks.

Using gruntcollection I can finally archieve it w/o the need to install those subtasks "locally". But a soon a I give it the keyword gruntcollection, I am not able to register Tasks directly in the composing-plugin