Allow connections from Mirakel.

Since inthe.am's internal taskd is version 1.0.0, clients other than taskwarrior have to be explicitly allowed. 

This addresses [MIR-532](https://mirakel.atlassian.net/browse/MIR-532).

On a server that's already running, updating the config and then sending SIGHUP should take care of it (and would be greatly appreciated even if this doesn't merge <3).

```bash
taskd config --force --data root/ client.allow '^task [2-9],^taskd,^libtaskd,^Mirakel [1-9]'
pkill -1 taskd
```