Several additional ES6 tests

This closes #98, #123, #133, #140, #141, #142, #143, #145, #146, #147, #148 and #152.

Added rows:
 * Proper tail calls
 * Shorthand properties
 * Shorthand methods
 * `__proto__` in object literals
 * `Object.getOwnPropertySymbols`
 * `Object.prototype.__proto__`
 * `Function.prototype.toMethod`
 * `String.raw`
 * `Symbol.create`
 * `Symbol.hasInstance`
 * `Symbol.isConcatSpreadable`
 * `Symbol.isRegExp`
 * `Symbol.iterator`
 * `Symbol.toPrimitive`
 * `Symbol.toStringTag`
 * `Symbol.unscopables`
 * `RegExp.prototype.match`
 * `RegExp.prototype.replace`
 * `RegExp.prototype.search`
 * `RegExp.prototype.split`
 * `Array.prototype.copyWithin`
 * `Array.prototype.keys`
 * `Array.prototype.values`
 * `Array.prototype.entries`

Also fixed a few existing tests and updated several source links.

I should note that I did not test RhinoJS, PhantomJS or IE11. I couldn't compile EchoJS but inferred support from reading the source. For historical versions of each browser, I used browsershots.com.