update docs / example title for colring

examples/colored.py

 #!/usr/bin/env python2
 """
-Masked wordcloud
-================
-Using a mask you can generate wordclouds in arbitrary shapes.
+Image-colored wordcloud
+========================
+You can color a word-cloud by using an image-based coloring strategy implemented in
+ImageColorGenerator. It uses the average color of the region occupied by the word
+in a source image. You can combine this with masking - pure-white will be interpreted
+as 'don't occupy' by the WordCloud object when passed as mask.
+If you want white as a legal color, you can just pass a different image to "mask",
+but make sure the image shapes line up.
 """
 
 from os import path