Add README.md file

Add basic info. This file is automatically displayed on GitHub, and is
kind of de-facto standard for project documentation.

BUG=chromium:415466
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/657423002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24731 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

README.md

+V8 JavaScript Engine
+=============
+
+V8 is Google's open source JavaScript engine.
+
+V8 implements ECMAScript as specified in ECMA-262.
+
+V8 is written in C++ and is used in Google Chrome, the open source
+browser from Google.
+
+V8 can run standalone, or can be embedded into any C++ application.
+
+V8 Project page: https://code.google.com/p/v8/
+
+
+Getting the Code
+=============
+
+V8 Git repository: https://chromium.googlesource.com/v8/v8.git
+GitHub mirror: https://github.com/v8/v8-git-mirror
+
+For fetching all branches, add the following into your remote
+configuration in `.git/config`:
+
+        fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
+        fetch = +refs/tags/*:refs/tags/*