Remove Hacktoberfest

It's almost at an end, so we can remove this.

README.md

@@ -16,11 +16,6 @@ Prometheus' main distinguishing features as compared to other monitoring systems
 - multiple modes of **graphing and dashboarding support**
 - **federation support** coming soon
 
-## Hacktoberfest 2015
-
-Prometheus is a featured project in [DigitalOcean's Hacktoberfest](https://hacktoberfest.digitalocean.com/). 
-We have prepared a [list of potential projects](https://docs.google.com/document/d/1u1iPsFZ0kaa1SJZ1BKoNdm0j5c2lxB1pFah1b4Na8Sg/edit#heading=h.lgmt23h6abgp) to get you started.
-
 ## Architecture overview
 
 ![](https://cdn.rawgit.com/prometheus/prometheus/e761f0d/documentation/images/architecture.svg)