async+perf: ch4, tweaks and clarifications to generators-as-iterators discussions
Typo fix: they've --> they're
Merge pull request #214 from tomsugden/patch-1

Typo fix: they've --> they're
async+perf: ch4, adding 'Iterating Generators Asynchronously' and 'Generators + Promises' discussions
this+object prototypes: from @mrkiffie, This is a retrofit collection of typo fixes, closes #216
async+perf: ch4, more on 'synchronous error handling'
async+perf: ch4, adding 'multiple iterators' section
async+perf: added more discussion for 'generators + promises' and 'promise-aware generator runner'
Fixed copy & paste error: failure -> filfillment

Instead of describing first `.then()`argument as 'fulfillment handler' a name of 'failure handler' was used probably due to copying the comment from the previous example.
Merge pull request #218 from jrencz/master

Fixed copy & paste error: failure -> filfillment
Fixed Promise#race() examples

Promise#race() accepts a single iterable, not the arbitrary amount of arguments
Merge pull request #219 from jrencz/race-fix

Fixed Promise#race() examples
async+perf: ch4, adding 'async / await' section
async+perf: ch3, 'thenable duck-typing', ch4 tweak
async+perf: ch4, adding 'promise concurrency in generators' section
async+perf: ch4, added lots of content to 'generator delegation' section
async+perf: ch4, tweaking some wording
async+perf: ch4, adding 'exceptions delegated' section, as well as discussion of delegating to non-generator iterators
async+perf: ch4, clarifying exception generator behavior
fix(typo)

Forgot a parenthesis