Add shorthand "prose hooks" for performing various operations

[domenic]

People seem confused, and want to know how they can do Promise.reject or Promise.all in their specs. It's pretty straightforward; you say:

Let x be the result of Promise.reject(r), using the initial value of Promise.reject.

But we may want to provide some easy phrases that are shorthand for this longhand. Here's what I can think of:

• a promise resolved with x (e.g. "return a promise resolved with x," "let p be a promise resolved with x")
• a promise rejected with r
• cast x to a promise
• let p be a newly-created promise object (the ES spec already uses this as shorthand for some crazy @@create stuff)
• resolve p with x
• reject p with r
• let p be the result of (racing p1, p2, p3 / racing iterableOfPromises)
• let p be the result of waiting for all of (p1, p2, p3 / iterableOfPromises) (any better phrasing?)

[annevk]

• Let p be the first of p1, p2, p3
• Let p be all of p1, p2, p3

[tabatkins]

"be the first of" is extremely ambiguous in English - it sounds like it's just referring to p1 in a stupid way. I prefer Domenic's wording.

Same with "let p be all of ..." - sounds like it's just collecting them into a list or something. "waiting for all" it a little long, but it's clear and easy to remember, so I'm fine with it.

[domenic]

Added a guide with these plus some guidance and examples. Could probably use more examples; pull requests welcome in that department.