upgrade browserify to 6.1.0
but we need a new release of es6ify before we want to merge this upgrade
move bounds calculation into Scene (no need to set it explicitly anymore)
update tests to match
Merge branch 'master' into bounds
upgrade jshint
Merge branch 'master' into upgrade-browserify
upgrade es6ify
Merge pull request #39 from tangrams/upgrade-browserify

Upgrade browserify to 6.1.0
merge master & update tests