Update README with barebones instructions on how to build JsAction with open-source compiler.
Update README with barebones instructions on how to build
JsAction with open-source compiler.

	Change on 2014/05/23 by nnaze <nnaze@google.com>

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=67866714

google/jsaction,google/jsaction