Remove Logc and friends

We never use them.  If you think you need one, consider passing a Stringer to
Logf (or friends) instead.
Remove XML configuration & output

YAGNI.
Merge pull request #8 from kevinwallace/remove_xml

Remove XML configuration & output
Merge pull request #6 from kevinwallace/remove_logc

Remove Logc and friends
Remove FINEST and TRACE levels

YAGNI.