ME: clicking 'x' button hides the welcome meessage
ME|RR: hiding welcome message when home page is accessed again
ME|RR: welcome message hidden permanently after being closed initially
ME|RR: added a callback to 'get-url' implementation
RR: use dommy/hide! instead of dommy/set-style!
Merge pull request #669 from onaio/585_add_close_event_to_x_button

585 add close event to x button