Add support for new showOverlay and hideOverlay methods.
Merge branch 'master' of https://github.com/globexdesigns/doby-grid

# By globexdesigns
# Via globexdesigns
* 'master' of https://github.com/globexdesigns/doby-grid:
  #56 New canvasFocus option prevents the grid from stealing focus on mouseenter
"Empty" notice is now drawn as an overlay instead of a row