Fix issues raised by go vet
Fixed a conflation of types between a filename and the *config.Config (source
and target).  The fmt was using a %s and meant the filename but used the nil
*config.Config

Removed an erroneous strconv.Itoa.  The fmt was using %d anyway.
Use Errorf and lowerCamel
Merge pull request #17 from mordyovits/go-vet-try3

Fix issues raised by go vet