This past June, Gmail launched its top-to-bottom redesign of its iOS app, but that doesn't mean it can't already be improved. Google has released Version 2.4 of the email app, bringing with it the addition of increased integration with Drive and Google+. Now when you send a link in-app to one of those platforms, those links will open in their respective apps. This will be particularly useful when sharing documents and spreadsheets from one Drive to another.
If, for some savage reason, you'd rather keep these links opening up in the web, you can update the app's settings. But why would you do such things?
Version 2.4 also includes a new, enhanced attachment experience, providing larger thumbnails that can be opened up for a full-screen viewing experience. You can find the latest version of Gmail for iOS, as always, in the App Store.