Refactored the API, moving it into a single api.js file which can be

exluded from a build if desired.

tasks/generate/js_api/templates/enum.param.tmpl

@@ -0,0 +1,8 @@
+if (_.contains(<%= _.camelCase(name) %>Options, <%= get %>)) {
+  <%= set %> = <%= get %>;
+} else {
+  throw new TypeError(
+    'Invalid <%= name %>: ' + <%= get %> +
+    ' should be one of ' + <%= _.camelCase(name) %>Options.join(', ') + '.'
+  );
+}