added a link to the world examples in the readme.

Also clarified an error message

README.rst

@@ -12,6 +12,9 @@ resolution images. It performs a similar function to the existing Minecraft
 Cartographer program but with a slightly different goal in mind: to generate
 large resolution images such that one can zoom in and see details.
 
+See some examples here!
+http://github.com/brownan/Minecraft-Overviewer/wiki/Map-examples
+
 Features
 ========
 

textures.py

@@ -61,7 +61,7 @@ def _find_file(filename, mode="rb"):
     if os.path.exists(path):
         return open(path, mode)
 
-    raise IOError("Could not find the file {0}".format(filename))
+    raise IOError("Could not find the file {0}. Is Minecraft installed? If so, I couldn't find the minecraft.jar file.".format(filename))
 
 def _load_image(filename):
     """Returns an image object"""