Fixing some minor code style issues in the runtime.
Use a less-clever for-loop to reset temporary context variables.

This style also saves six gzip'd bytes.
Regenerate runtime/min.js from runtime/dev.js.

Command used:
uglifyjs dev.js --mangle --compress --comments /Copyright/ --output min.js
Merge pull request #1 from facebook/runtime-style-tweaks

Counter pull request!
Merge pull request #37 from cpojer/master

Fixing some minor code style issues in the runtime.