Update contributing guide to remove gerrit.

The contributors list is outdated, update. Looks like we're sorting by first name.

CONTRIBUTING.md

@@ -1,30 +1,11 @@
 # Contributing
 
-Prometheus uses Gerrit to manage reviews of pull-requests, and then
-Gerrit replicates its master branch to GitHub. In order to contribute to
-Prometheus, you must use Gerrit.
-
-## Setup
-
-1. Sign in at http://review.prometheus.io/
-2. Set a username and upload an SSH pubkey for git ssh access.
-
-   On OSX you can use `cat ~/.ssh/id_rsa.pub | pbcopy` to copy your public key
-   to your clipboard so you can paste it.
-3. Clone the repo: `git clone http://review.prometheus.io/prometheus`
-4. Add your user-specific remote that you will push your changes to:
-   `git remote add <your-remote-name> ssh://<username>@review.prometheus.io:29418/prometheus`
-5. Add Change-Id commit hook: `curl -o .git/hooks/commit-msg http://review.prometheus.io/tools/hooks/commit-msg`
-6. Make the file executable: `chmod u+x .git/hooks/commit-msg`
-7. Commit any local changes to git, then:
-8. `git push <your-remote-name> HEAD:refs/for/master`
-9. Assign reviewer for change at http://review.prometheus.io/
+Prometheus uses GitHub to manage reviews of pull-requests.
 
 ## Getting Started
 
 1. Reach out via our [mailing list](https://groups.google.com/forum/?fromgroups#!forum/prometheus-developers) and ask us what
-   the current priorities are.  We can find a good isolated starter project for
-   you.
+   the current priorities are. We can find a good isolated starter project for you.
 
 2. Keeping code hygiene is important.  We thusly have a practical preference
    for the following:

CONTRIBUTORS.md

@@ -1,4 +1,6 @@
 # Prometheus Team
+- Björn Rabenstein
+- Brian Brazil
 - Johannes Ziemke
 - Julius Volz
 - Matt T. Proud