v3.0.0 - IE8 & 9 support dropped; stagger option

• 🔧 Added stagger option to stagger item transitions. Fixed #1019
• 📦 Improved Webpack config
• ✂️ Removed IE8 & 9 code
  • ✂️ removed IE8 dependencies: classie, eventie, get-style-property
• ⬆️ outlayer v2.
  • replaced EventEmitter with smaller ev-emitter
  • use [data-isotope] to init in HTML. .js-isotope & data-isotope-options still works
  • isOption changed to option. Maintain backwards compatibility with old isOption names:
    • isOriginLeft -> originLeft
    • isOriginTop -> originTop
    • isResizeBound -> resize
    • isInitLayout -> initLayout
• ⬆️ jquery-bridget v2. Changed jquery.bridget.js path to jquery-bridget.js
• ⬆️ get-size v2
• 🍹 switched out Grunt for Gulp for tasks