Document release process.

Fixes #292.

This is mostly an initial sketch for discussion.

This also at least partially addresses #86, #87, #126, #277.
This step failed on my F20 laptop.

```
[~]$ sudo yum localinstall http://archive.clusterhq.com/fedora/flocker-release$(rpm -E %dist).noarch.rpm
[sudo] password for richard: 
Loaded plugins: langpacks, refresh-packagekit
Cannot open: http://archive.clusterhq.com/fedora/flocker-release.fc20.noarch.rpm. Skipping.
Nothing to do
```

```
[~]$ curl http://archive.clusterhq.com/fedora/flocker-release.fc20.noarch.rpm
<?xml version='1.0' encoding='UTF-8'?><Error><Code>NoSuchKey</Code><Message>The specified key does not exist.</Message></Error>
```