Added save as functionality to UI

[Plumpernickel]

No description provided.

[humphd]

Don't do this up here, make it a local variable in showSaveDialog

[humphd]

Change this to:

+ function showSaveDialog(title, initialPath, defaultName, callback) {
+     var selectedPath;
+     var saveResponse = window.prompt(title, defaultName);
+     if(saveResponse){
+         initialPath = initialPath || '/';
+         selectedPath = initialPath + saveResponse;
+         callback(null, selectedPath);
+     } else {
+        // User hit cancel
+        callback();
+     }
+ }

[humphd]

Change to 4-space indents please, to match the rest of the file. r=me with that fix.