implemented most of the new API by delegating to existing functionality
handled branching between deprecated and new implementation for binding of dom methods
implemented style value getter
replacing legacy method with more single purpose methods
Adding style value getter with support for fetching multiple styles at once
updated docs
updated docs
Merge branch 'prefixer-api-update' of https://github.com/Financial-Times/o-useragent into prefixer-api-update

Conflicts:
	README.md
	src/js/prefixer.js