Revert "clean the working tree before Travis", that wasn’t helpful…

mirabilos · mirabilos · commit 548cbc0452a0 · 2017-09-22T23:55:54.000+02:00
This reverts commit fb167e2.
diff --git a/.travis.yml b/.travis.yml
@@ -2,5 +2,4 @@ language: node_js
 node_js:
   - "6.11.3"
 before_script:
-  - git clean -fdx
   - npm install -g grunt-cli
