Fix connection failing when not provided in an IP address form

[paked]

Connecting currently breaks if the channel_key is provided in any form that isn't an IPv4 address.

This is because of the way ParseChannelKey works. It uses fmt.Sscanf with a format which pulls four specific numbers (representing the four sections of an IPv4 address).

I would like to experiment parsing it with net/url. As it is roughly a URL form. If that doesn't work we may have to change the Channel Key schema.