build: Post release bump to 1.3.7
build: Post release bump to 1.3.7

GNOME/clutter-gst,GNOME/clutter-gst,skinkie/clutter-gst,skinkie/clutter-gst,lubosz/clutter-gst,lubosz/clutter-gst,ystreet/clutter-gst,ystreet/clutter-gst,lubosz/clutter-gst,ystreet/clutter-gst,GNOME/clutter-gst,skinkie/clutter-gst,ystreet/clutter-gst,GNOME/clutter-gst