pep8analysis: use Google Analytics asynchronously

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
Merge: pep8analysis: use Google Analytics asynchronously

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

Pull-Request: #547
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>