Update .travis.yml

Don't build on docker image on each stages

.travis.yml

@@ -6,9 +6,7 @@ go_import_path: github.com/ethereum/go-ethereum
 services:
   - docker
 
-before_install:
-  - docker build -t enapoleone/tomochain .
-  - docker run enapoleone/tomochain
+before_install: true
 
 jobs:
   include:
@@ -33,14 +31,6 @@ jobs:
     - sudo chown root:$USER /etc/fuse.conf
     - go run build/ci.go install
     - go run build/ci.go test -coverage
-  - os: osx
-    go: '1.10'
-    script:
-    - unset -f cd
-    - brew update
-    - brew cask install osxfuse
-    - go run build/ci.go install
-    - go run build/ci.go test -coverage
   - stage: Lint
     os: linux
     dist: trusty
@@ -52,6 +42,9 @@ jobs:
     script:
     - go run build/ci.go lint
   - stage: Push Docker image
+    before_install:
+      - docker build -t enapoleone/tomochain .
+      - docker run enapoleone/tomochain
     deploy:
       provider: script
       script: bash docker_push