Issue #84 - Update Robot Framework to version 3.0.4

* Updated the Dockerfile

Author: ppodgorsek

Dockerfile

@@ -17,7 +17,7 @@ ENV CHROMIUM_VERSION 65.0.*
 ENV FAKER_VERSION 4.2.0
 ENV FIREFOX_VERSION 59.0*
 ENV GECKO_DRIVER_VERSION v0.19.1
-ENV ROBOT_FRAMEWORK_VERSION 3.0.2
+ENV ROBOT_FRAMEWORK_VERSION 3.0.4
 ENV SELENIUM_LIBRARY_VERSION 3.1.1
 
 # Install system dependencies