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
Merge pull request #222 from mallowigi/patch-1

fix(typo)
async+perf: tweaking terminology for consistency
async+perf: ch4, starting 'pre es6 generators' section
async+perf: ch4, finishing 'pre-es6 generators' discussion
async+perf: ch3, clarifying 'promise cancelation'
async+perf: ch4, adding 'generator concurrency' section, tweaking values across chapter demos for consistency
async+perf: ch4, adding more clarifying details about generator interleaving/concurrency
async+perf: adding skeletons for ch5 and ch6
this+object prototypes: ch2, fixing typo 'obj' instead of 'foo', closes #224
fix typo

ECMASCript --> ECMAScript
fix typo: forsee --> foresee
Merge pull request #225 from cncolder/patch-1

fix typo
async+perf: ch4, starting 'thunk' section