upload: Move compose initialization back to compose module.

This makes the lines of logic a bit simpler.

static/js/compose.js

@@ -1027,7 +1027,9 @@ exports.initialize = function () {
         Dropbox.choose(options);
     });
 
-    upload.initialize();
+    $("#compose").filedrop(
+        upload.options()
+    );
 
     if (page_params.narrow !== undefined) {
         if (page_params.narrow_topic !== undefined) {

static/js/upload.js

@@ -127,12 +127,6 @@ exports.options = function () {
     };
 };
 
-exports.initialize = function () {
-    $("#compose").filedrop(
-        exports.options()
-    );
-};
-
 return exports;
 }());