Updated grunt proxy server to rewrite to WSGI in dev

When running storyboard as a developer, we run into a bit of a problem with
the apache mod_wsgi config (which prefixes a context root of /api/v1) vs.
our simple-server setup (which uses /v1 as a context root). Since this only
impacts the grunt server running locally, it seems appropriate to simply
rewrite the grunt CORS-buster proxy to handle this for us.

Change-Id: Iec9454c845a880f383a8c3a7bfc15db58101d549

Gruntfile.js

@@ -408,10 +408,13 @@ module.exports = function (grunt) {
             },
             proxies: [
                 {
-                    context: '/v1',
+                    context: '/api/v1',
                     host: 'localhost',
                     port: 8080,
-                    https: false
+                    https: false,
+                    rewrite: {
+                        '^/api/v1': '/v1'
+                    }
                 }
             ],
             livereload: {