Update RF to 3.1.0 in Travis (#1256)

Author: aaltat

.travis.yml

@@ -22,29 +22,29 @@ matrix:
       env:
         - BROWSER=headlesschrome
         - SELENIUM=3.141.0
-        - ROBOTFRAMEWORK=3.0.4
+        - ROBOTFRAMEWORK=3.1.0
         - ROBOT_OPTIONS=--dotted
         - INTERPRETER=python3
     - python: "pypy3.5"
       env:
         - BROWSER=chrome
         - SELENIUM=3.141.0
-        - ROBOTFRAMEWORK=3.0.4
+        - ROBOTFRAMEWORK=3.1.0
         - ROBOT_OPTIONS=--dotted
         - INTERPRETER=pypy3
     - python: "3.6"
       env:
         - BROWSER=headlesschrome
         - SELENIUM=3.141.0
-        - ROBOTFRAMEWORK=3.0.4
+        - ROBOTFRAMEWORK=3.1.0
         - ROBOT_OPTIONS=--dotted
         - INTERPRETER=python3
         - JYTHON=true
     - python: "3.4"
       env:
         - BROWSER=headlesschrome
         - SELENIUM=3.141.0
-        - ROBOTFRAMEWORK=3.0.4
+        - ROBOTFRAMEWORK=3.1.0
         - ROBOT_OPTIONS=--dotted
         - INTERPRETER=python3
     - python: "2.7"