Added client class, for multiple config support

Closes #4

LGTM given by: @marten

Squashed commit of the following:

commit 582ba239654ef04a3bf2189e3a59b97283dea7bb
Author: Henk <henk.van.der.veen@gmail.com>
Date:   Wed Jan 29 16:06:37 2014 +0100

    moved code for A19#fetch to client and always using a client in the fetcher

commit 6500baa0992f9b3d17e9dc9b1a26f64f2276b688
Author: Henk <henk.van.der.veen@gmail.com>
Date:   Tue Jan 28 15:42:28 2014 +0100

    Added client class, for multiple config support