Core: Dropping wrong argument on semaphore check

Fixes #550
Build: Update version from pre to -pre

Ref jquery/jquery-release#61
Build: use browserSets from config file; allow to override

Closes gh-552
Core: Pass total amount of tests to QUnit.begin callback as totalTests

Fixes gh-350
Closes gh-553
Core: Use Date.now when possible and normalize on new Date().getTime()

Fixes gh-544
Closes gh-545
README: Fix Grunt installation command