fotogrid: make pycodestyle happy

make test complains:
  $ make test
  pycodestyle *.py
  fotogrid.py:3:1: E302 expected 2 blank lines, found 0
  make: *** [Makefile:17: test] Error 1

This is because pycodestyle interprets the function documentation as
python shebang line or module documentation and expects two blank lines
afterwards.

Move the function documentation into python heredoc.

Signed-off-by: Johannes Thumshirn <jth@kernel.org>

fotogrid.py

@@ -1,6 +1,8 @@
-# Provide a simple responsive fotogrid using flex layout.
-# Depends on the css/fotogrid.css defined styles.
 def fotogrid(image_urls):
+    """
+    Provide a simple responsive fotogrid using flex layout.
+    Depends on the css/fotogrid.css defined styles.
+    """
     result = '<div class="fotorow">'
     cols = 4
     images = divmod(len(image_urls), cols)