Weekly release v0.2.43: Testing improvements and various optimizations.

Summary:
stop abstract loops from getting stuck in infinite loops when body contains a return, throw or break completion
Object.assign should no longer lose values when snapshotting in certain cases
Allow __optimize to work in conditional contexts
Move abstract Object.assign temporals into a helper function
new color scheme for the website
Add ability to rewrite generated code via global.__output
adds an optimization to Object.assign that attempts to merge calls together where possible
Added --expectedCounts parameter to test262-runner so that success can depend on the value of the time-out and the version of the test suite that is used.
Updated the test262 submodule to latest version

Reviewed By: cblappert

Differential Revision: D8837068

fbshipit-source-id: 218879046dbb0e307cbf3a13ba9a66d11e99a3f0

package.json

@@ -1,6 +1,6 @@
 {
   "name": "prepack",
-  "version": "0.2.43-alpha.0",
+  "version": "0.2.43",
   "description": "Execute a JS bundle, serialize global state and side effects to a snapshot that can be quickly restored.",
   "homepage": "https://github.com/facebook/prepack",
   "repository": {