docd/appengine: bump to 1.3.7 (#146)

Author: jonathaningram

docd/appengine/Dockerfile

@@ -1,5 +1,5 @@
 # Dockerfile which produces an AppEngine custom runtime containing docd and all
 # of its runtime dependencies.
 # https://cloud.google.com/appengine/docs/flexible/custom-runtimes/about-custom-runtimes
-FROM sajari/docd:1.3.5
+FROM sajari/docd:1.3.7
 CMD ["-addr", ":8080", "-error-reporting"]