Reduce the number of tests run in the unit testing stage to speed up Travis builds.

Author: kernelmethod

.travis.yml

@@ -1,35 +1,25 @@
 language: julia
 
+os: linux
+dist: bionic
+
 notifications:
   email: false
 
 jobs:
+
   allow_failures:
-    - julia: 1.0
-    - julia: 1.1
-    - julia: 1.2
     - julia: 1.4
     - julia: nightly
-    - os: osx
-    - os: windows
+
   include:
-    ###### Tests
-    ### Linux
-    - stage: "Unit tests"
-      julia: 1.0
-      os: linux
 
-    - stage:
-      julia: 1.1
-      os: linux
+    ########################################################
+    ### Unit testing
+    ########################################################
 
-    - stage:
-      julia: 1.2
-      os: linux
-
-    - stage:
+    - stage: "Unit testing"
       julia: 1.3
-      os: linux
       after_success:
         # Code coverage
         - julia -e 'using Pkg; Pkg.add("Coverage");'
@@ -38,35 +28,16 @@ jobs:
 
     - stage: 
       julia: 1.4
-      os: linux
-
-    - stage: # Unit tests
-      julia: nightly
-      os: linux
 
-    ### OSX
-    - stage: # Unit tests
-      julia: 1.3
-      os: osx
-
-    - stage: # Unit tests
-      julia: nightly
-      os: osx
-
-    ### Windows
-    - stage: # Unit tests
-      julia: 1.3
-      os: windows
-
-    - stage: # Unit tests
+    - stage:
       julia: nightly
-      os: windows
 
+    ########################################################
     ### Documentation generation
+    ########################################################
+
     - stage: "Documentation"
       julia: 1.3
-      os: linux
-      dist: bionic
       install:
         - sudo apt-get update
         - sudo apt-get install -y python3.7 python3-pip python3-setuptools