all typos
tip format for intro
Merge pull request #5 from chenglou/moremore

correct all typos; add intro tip format
props in `getInitialState` as anti-pattern
Merge pull request #6 from chenglou/last-few

props in `getInitialState` as anti-pattern
shrink working on props in state entry
Add event listeners cookbook entry
modify some wording
Merge pull request #7 from chenglou/last-few

modify some wording