WA-238 Running optmized improvements of safe contracts

.travis.yml

@@ -4,10 +4,11 @@ node_js:
 os:
   - linux
 before_script:
-  - yarn global add truffle@4.1.3
+  - yarn global add truffle@4.1.5
   - yarn global add surge
   - git clone https://github.com/gnosis/gnosis-safe-contracts.git
   - cd gnosis-safe-contracts
+  - git fetch && git checkout feature/optimize_personal_edition
   - truffle compile && cd ..
 after_success:
   - yarn build-storybook