refactor, interface cleanup, update docs
some minor tweaks

* drop legacy support for "setValAttrPropPref"
* re-introduce "stringify" method (alias for jsToString endpoint)
* code style (indention = 2 spaces, as in original MDN code
Merge branch 'igord-master'
use global window object if present (restores compatibility with browserify)
drop legacy IE support
Merge remote-tracking branch 'upstream/master'

Conflicts:
	index.js
remove unneeded data
added conversion example