Make `jake runtests-browser` support test regexes with spaces

For example: `jake runtests-browser t="transpile .js files"` now works.

Jakefile.js

@@ -855,7 +855,7 @@ task("runtests-browser", ["tests", "browserify", builtLocalDirectory, servicesFi
     }
 
     tests = tests ? tests : '';
-    var cmd = host + " tests/webTestServer.js " + port + " " + browser + " " + tests;
+    var cmd = host + " tests/webTestServer.js " + port + " " + browser + " " + JSON.stringify(tests);
     console.log(cmd);
     exec(cmd);
 }, {async: true});