Add few arbitrary apps to 'bmo sensible'

dotfiles/config/bmo/sensible.ini

 [sensible.gui]
 
     browser = vimb
+    browser = servo
     browser = dillo
     browser = uzbl-browser
     browser = surf
     editor = mousepad
     editor = gvim
     editor = gedit
+
+    image-viewer = ristretto
+
+    opener = xdg-open