drop 3.5 as it is least used per https://pypistats.org/packages/__all__; keep 3.4 to guard against regression as it is earliest 3.x release supported. Add 3.9 now that it is GR. add nightly,

Author: rouilj

.travis.yml

@@ -7,11 +7,11 @@ cache: pip
 python:
   - 2.7
   - 3.4
-  - 3.5
   - 3.6
   - 3.7
   - 3.8
-#  - nightly
+  - 3.9
+  - nightly
 
 #I would like to build and test the maint-1.6 and trunk/default
 #but we need different environments for these: