Fleet MinSize needs to be greater than 1

Otherwise autoscaling will knock the fleet size down to MinSize when
Latency is low; DesiredCapacity only comes into play at Fleet creation
time, it seems.

This is a bugfix to #68; please do not merge it until you have taken a look at the deployment I'm kicking off:

```
"arn:aws:cloudformation:us-east-1:437323568624:stack/shuff2-mediawiki-production/aeccd7f0-2174-11e3-9381-500150b34c7c"
```

Please make sure that both tiers have at least two instances running.