fix travis for documentation build

.travis.yml

@@ -9,9 +9,8 @@ julia:
   - 1.3
   - nightly
 
-matrix:
-  allow_failures:
-    - julia: nightly
+notifications:
+  email: false
 
 jobs:
   include:
@@ -24,6 +23,5 @@ jobs:
         - julia --project=docs/ docs/make.jl
       after_success: skip
 
-## uncomment the following lines to override the default test script
-script:
- - julia --color=yes -e 'using Pkg; Pkg.activate(); Pkg.instantiate(); Pkg.test()'
+  allow_failures:
+    - julia: nightly