Added colon to title separation list.
Added colon to title separation list.

Can now also convert post titles following the following specification:
```
<prefix><episode-number>: <title>
```
podlove/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher