Merge branch 'core-js' into 2.0.0

Conflicts:
	lib/6to5/polyfill.js

lib/6to5/polyfill.js

@@ -1,53 +1,2 @@
-/* jshint newcap: false, freeze: false */
-
-var ensureSymbol = function (key) {
-  Symbol[key] = Symbol[key] || Symbol(key);
-};
-
-var ensureProto = function (Constructor, key, val) {
-  var proto = Constructor.prototype;
-  if (!proto[key]) {
-    Object.defineProperty(proto, key, {
-      value: val
-    });
-  }
-};
-
-//
-
-if (typeof Symbol === "undefined") {
-  require("es6-symbol/implement");
-
-  var globSymbols = {};
-
-  Symbol.for = function (key) {
-    return globSymbols[key] = globSymbols[key] || Symbol(key);
-  };
-
-  Symbol.keyFor = function (sym) {
-    return sym.__description__;
-  };
-}
-
-require("es6-shim");
-require("regenerator/runtime");
-
-ensureSymbol("species");
-
-// Abstract references
-
-ensureSymbol("referenceGet");
-ensureSymbol("referenceSet");
-ensureSymbol("referenceDelete");
-
-ensureProto(Function, Symbol.referenceGet, function () { return this; });
-
-ensureProto(Map, Symbol.referenceGet, Map.prototype.get);
-ensureProto(Map, Symbol.referenceSet, Map.prototype.set);
-ensureProto(Map, Symbol.referenceDelete, Map.prototype.delete);
-
-if (global.WeakMap) {
-  ensureProto(WeakMap, Symbol.referenceGet, WeakMap.prototype.get);
-  ensureProto(WeakMap, Symbol.referenceSet, WeakMap.prototype.set);
-  ensureProto(WeakMap, Symbol.referenceDelete, WeakMap.prototype.delete);
-}
+require("core-js/shim");
+require("./transformation/transformers/es6-generators/runtime");