Update .travis.yml

Author: theogf

.travis.yml

@@ -6,6 +6,7 @@ os:
 julia:
   - 1.2
   - 1.3
+  - 1.4
 #  - nightly
 #matrix:
 # allow_failures:
@@ -18,7 +19,7 @@ after_success:
 jobs:
   include:
     - stage: "Documentation"
-      julia: 1.1
+      julia: 1.4
       os: linux
       script:
         - export DOCUMENTER_DEBUG=true