Increment major version

Recent changes to the metadata for negative tests fundamentally alter
the way those tests are intended to be interpreted. Increment the
project's version number in order to signal this to project consumers.

package.json

 {
   "name": "test262",
-  "version": "1.0.0",
+  "version": "2.0.0",
   "description": "Test262 tests conformance to the continually maintained draft future ECMAScript standard found at http://tc39.github.io/ecma262/ , together with any Stage 3 or later TC39 proposals.",
   "repository": {
     "type": "git",