`Q.resolve` and `Q.when` to `Q`, where possible.

Inspired by https://github.com/kriskowal/q/pull/344#issuecomment-21127346.
Correct reference to C# version for the 'await' keyword
update Q.async to work with current ES6 generators without send()
Add async generators example to show composition with standard control flow
update old & new examples to use more of Q, and make new example more comprehensive