update travis

.travis.yml

@@ -1,9 +1,8 @@
 language: julia
 
 julia:
-  - 1.0
-  - 1.3
-  - 1.4
+  - 1     # current stable
+  - 1.0   # lts
   - nightly
 
 script:
@@ -15,11 +14,10 @@ after_success:
 
 jobs:
   allow_failures:
-    - julia: 1.4
     - julia: nightly
   include:
     - stage: "Documentation"
-      julia: 1.3
+      julia: 1
       os: linux
       script:
         - julia --project=doc/ -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd()));