0.7.2

• performance: convex hull calculation cythonized and extended for spherical
  coordinates
• performance: planar length calculations are much faster (~700 x) and geodetic
  length calculations are somewhat faster (~1.8 x)
• fix: CompressedBand now always returns array when indexed with a slice
• fix: output dimension of grid sampling methods is now always one larger than
  the input
• raster.merge now works with multiband grids
• efficient algorithm for intersection detection in planar and spherical
  coordinates
• new read_gtiffs function for reading multiple files as bands
• implement experimental RegularGrid.coordinates() method returning a
  CoordGenerator object
• implement get_coordinate_lists for Multiline and Multipolygon
• other performance optimizations and fixes