added GridRelease to easily make a gird of elements.
Merge branch 'master' of https://trac.orr.noaa.gov/git/PyGnome
fixed the bug in geo_json where the _next_output_time was not being
incremented
Merge branch 'master' of https://trac.orr.noaa.gov/git/PyGnome
fixed issue in RectangularGRidProjection -- no longer returns NaN when off grid. now clips to grid. This should perhaps be an extrapolation instead, but this works for now.
Merge branch 'master' into HEAD
Merge branch 'master' of https://trac.orr.noaa.gov/git/PyGnome