Add functions for calculating the times of sunrise and sunset.  TODO: This still needs to be implemented for when we don't have PyEphem.
Add functions for calculating the times of sunrise and sunset.  TODO: This still needs to be implemented for when we don't have PyEphem.

git-svn-id: acf0ef94bfce630b1a882387fc03ab8593ec6522@212 150532fb-1d5b-0410-a8ab-efec50f980d4

jrleeman/MetPy,dopplershift/MetPy,ahaberlie/MetPy,jrleeman/MetPy,Unidata/MetPy,ShawnMurd/MetPy,ahill818/MetPy,dopplershift/MetPy,ahaberlie/MetPy,Unidata/MetPy,deeplycloudy/MetPy