Set a never expire, cross sub-domain cookie for blocking analytics

Part of the work for:
https://www.pivotaltracker.com/story/show/75136808

Will use presence of this cookie to determine whether we should use analytics in Hydra
This feels like a nitpick... but it might be a bit less cognitive overhead to set some constants like `DAYS = 60 * 60 * 24` and then have `expires: Time.now + 7 * DAYS` and then `YEARS = 365 * DAYS` with the below reading `:expires => Time.now + 10 * YEARS`