Remove Dockerfile and Docker tests

Author: alex-lew

.travis.yml

@@ -7,17 +7,11 @@ julia:
   - 1.5
   - 1.6
 
-services:
-  - docker
-
 jobs:
   include:
     - stage: test
       script:
         - julia -e 'using Pkg; Pkg.build(); Pkg.test()'
-    - stage: docker
-      script:
-        - docker build docker/ -t gen
     - stage: docs
       julia: 1.6
       os: linux