2015-01-24 - This is an experimental version of OPT that adds support
for multiple target languages under one unified app. It relies on
Node.js for the server and docker for sandboxing

To install node dependencies, run 'make deps'

---
This directory provides only backends. Look in ../v3/ for frontend code

Once you start up the Node.js server, then you can ping it with
HTTP/HTTPS endpoints such as:

  /exec_java
  /exec_java_jsonp

to run various language backends, passing arguments in via GET
parameters. Each set of endpoints comes in a pair that returns either
regular JSON data (e.g., /exec_java) or JSONP (e.g., /exec_java_jsonp)
for cross-domain AJAX.


Look at variables such as JAVA_JSONP_ENDPOINT in
../v3/js/opt-frontend-common.js to see how the frontend calls the
backends via JSONP using jQuery code like:

      // the REAL call uses JSONP
      // http://learn.jquery.com/ajax/working-with-jsonp/
      assert(jsonp_endpoint);
      $.ajax({
        url: jsonp_endpoint,
        // The name of the callback parameter, as specified by the YQL service
        jsonp: "callback",
        dataType: "jsonp",
        data: {user_script : codeToExec,
               options_json: JSON.stringify(backendOptionsObj)},
        success: execCallback,
      });