n+1 queries on Addresses#index

[joshsmith]

You can see from New Relic that we're getting n+1 queries on Addresses by asking for n+1 Users and Visits. No bueno.

[joshsmith]

For users this causes this lovely 503 error every time they zoom out and look at the map. What should be inspiring is now frustrating.

[christopherstyles]

@joshsmith Is this still an issue? (It was mentioned in #111 that it had been solved along with that PR?)