initial support for browser environment

test fails because of global variable caught by mocha!

currently very big file size but we can blame jsonld.js :wink: 
i would keep #3 open to track further improvements including help with refactoring jsonld.js!

i moved fixtures into helper.js file to work around issues with zuul + brfs
i also moved require('chai').expect to each file so zuul doesn't complain
would like to make a dedicated issue soon to refactor test where we could take care of cleaning that up....