Added Migurski/ OSM Terrain for the US

build.out

@@ -0,0 +1,4 @@
+running build
+running build_py
+running build_ext
+cythoning lib/cartopy/trace.pyx to lib/cartopy\trace.cpp

lib/cartopy/io/img_tiles.py

@@ -225,6 +225,31 @@ def _image_url(self, tile):
         return url
 
 
+class StamenTerrain(GoogleTiles):
+    """
+    Terrain tiles defined for the continental United States, and include land
+    color and shaded hills. The land colors are a custom palette developed by
+    Gem Spear for the National Atlas 1km land cover data set, which defines
+    twenty-four land classifications including five kinds of forest,
+    combinations of shrubs, grasses and crops, and a few tundras and wetlands.
+    The colors are at their highest contrast when fully zoomed-out to the
+    whole U.S., and they slowly fade out to pale off-white as you zoom in to
+    leave room for foreground data and break up the weirdness of large areas
+    of flat, dark green.
+
+    Additional info:
+    http://mike.teczno.com/notes/osm-us-terrain-layer/background.html
+    http://maps.stamen.com/#terrain/12/37.6902/-122.3600
+    http://wiki.openstreetmap.org/wiki/List_of_OSM_based_Services
+    https://github.com/migurski/DEM-Tools
+    """
+    def _image_url(self, tile):
+        x, y, z = tile
+        url = 'http://tile.stamen.com/terrain-background/%s/%s/%s.png' % (
+            z, x, y)
+        return url
+
+
 class QuadtreeTiles(GoogleTiles):
     """
     Implements web tile retrieval using the Microsoft WTS quadkey coordinate