Complete Google Analytics integration

[abhinavpappu]

Limited support for Google Analytics has already been added in order to track document accesses. Currently it only records pageviews when the user visits a static document such as https://hackillinois.org/sponsor. The code added to enable that can be seen here: HackIllinois/site@77e5707.

The main thing that needs to be added is:

• Page tracking for all pages (ideally this should be integrated with React Router so that we don't have to modify every page component)

Another thing we may want is tracking mobile sign ins (so this would be in the Auth component and we would probably want to create a Google Analytics event with "android" or "ios").

And feel free to add anything else that might be useful to track.