Use named stages

Author: florimondmanca

.travis.yml

@@ -14,9 +14,12 @@ python:
 
 matrix:
   include:
-    - python: 3.7
+    -
+      stage: Check
+      python: 3.7
       script: scripts/check
-    - python: 3.7
+    - stage: Docs
+      python: 3.7
       script: scripts/docs
     - os: windows
       language: shell