drop julia 1.0, 1.2, 1.3 from travis

.travis.yml

@@ -4,10 +4,8 @@ os:
   - linux
   - osx
 julia:
-  - 1.0
-  - 1.1
-  - 1.2
   - 1.3
+  - 1.4
   - nightly
 notifications:
   email: true
@@ -16,8 +14,4 @@ matrix:
   allow_failures:
     - julia: nightly
 
-## uncomment the following lines to override the default test
-# script:
-  # - julia -e 'Pkg.clone(pwd()); Pkg.build("Groups"); Pkg.test("Groups"; coverage=true)'
-
 codecov: true