Add docs for Task members
Add docs for Task members

- isRunning
- isQueued
- isIdle
- state
- last
- lastRunning
- lastPerformed
- lastSuccessful
- lastComplete
- lastErrored
- lastCanceled
- lastIncomplete

machty/ember-concurrency,machty/ember-concurrency,machty/ember-concurrency,machty/ember-concurrency