Typo fix
Removed vestigial #include GPSconfig.h

#include "GPSconfig.h" is leftover from some earlier version. Since the
fie is no longer in the library, it causes a compilation error
Fixed Serial1 references in leo_echo sketch
Merge pull request #19 from jrcutler/patch-1

Correct checksum on $PMTK001,161,3
fix PGCMD_NOANTENNA checksum

PGCMD_NOANTENNA checksum was wrong.