Stop transforming class -> className

Update the broken examples too (`git grep class=`)
Warn for 'class' and 'for' property names

Also stroke-linecap, stroke-width, stop-color, stop-opacity.

Test Plan:
grunt test
Fix input/textarea `value` of number 0 and `false`

Previously, setting textarea `value` to number 0 is treated as if `value` wasn't set at all (thus the textarea is cleared from 0 to '' upon `onChange`). `false` also renders as `"false"` instead of `""` for both `defaultValue` and `value`, on textarea _and_ input.
Merge pull request #328 from zpao/no-transform-class

Stop transforming class -> className
Merge pull request #330 from spicyj/warn-class-for

Warn for 'class' and 'for' property names
Merge pull request #274 from chenglou/textarea-patch

fix textarea `value` of number 0