Merge pull request #99 from redding/kr-config-hsots

move sanford config and hosts util classes into their own files
configure template sources

This updates the config API to allow configuring template sources.
This is part of the effort to add a render pipeline to Sanford.  To
render a template, it needs to exist in a configured source.

Note, this involved changing the config proxy to a class instance
implementation.  This instance will track the sources.  I also updated
the configs tests to work accordingly and made them more robust.