[travis] *py*yaml it is

.travis.yml

@@ -10,7 +10,7 @@ install:
   - pip install i3ipc
   - pip install psutil
   - pip install netifaces
-  - pip install yaml
+  - pip install pyyaml
   - pip install -U coverage==4.3
   - pip install codeclimate-test-reporter
 script: