Deki Wiki "Hayes" includes out-of-the-box support for Google Analytics. So you can easily track how popular your wiki is, where the traffic is coming from, and many page hits you get.
To enable Google Analytics, go to Tools > Control Panel > Site Settings.

Enter your Google Analytics code. And click Start Tracking. Voilà, your site is now setup for tracking your site statistics on Google Analytics!
If you don't want to use Google Analytics, just leave the box blank and it will be disabled.
And no, Analytics will not let you track downloads.