async+perf: ch3, wording tweaks
async+perf: ch3, promise patterns
Typo Fix: overriden > overridden
Typo Fix: ther > the
Typo Fix: assigment > assignment
Typo Fix: statment > statement
async+perf: ch3, more on 'promise patterns'
async+perf: ch3, tweaks to wording
async+perf: ch3, starting 'limitations' discussion
core README tweak
async+perf: ch3, more on promise limitations
async+perf: ch3, finishing 'limitations' section
types+grammar: appendixA, fixing code typo, per @qgustavor
async+perf: starting ch4 'generators'
async+perf: ch4, starting 'breaking run-to-completion' section
Fixed a tiny typo
Merge pull request #212 from HugoGiraudel/patch-1

Fixed a tiny typo
async+perf: starting 'input + output' section
async+perf: ch4, more on 'iteration messaging' and 'tale of two questions'
async+perf: ch4, tweaks and clarifications