Incoming swath coordinates might be fractional.  Use the the nearest
integral swath coordinates to generate the domainSet.  This maintains
a consistency with the geolocation.  This was a nasty little one because
the navigation error usually was less than a pixel, and just not
noticeable with high-res imagery.
Merge pull request #15 from tomrink/master

SwathAdapter: fractional to integral swath coordinates.