.jshintrc: set browser:false

Setting `browser:true` predefines a large list of globals. Some of
these, like `window`, `location`, and `setTimeout`, are really useful.
Some of them, like `name` and `event` are really dangerous to have
available as globals. They invite code errors.
Merge pull request #2953 from jamesarosen/james/jshint_browser

.jshintrc: set browser:false