Add posibility to force redraw.

Relating to this stackoveflow entry: http://stackoverflow.com/questions/22066261/handsontable-doesnt-appear-before-click-or-some-other-operation/22070768#22070768

I had an issue using handsontable with backbone.

I run the plugin on element not attached to the dom, and it doesn't show until I click on the table.
I tried to do ht.render() but it didn't work. Adding the parameter for FORCE option solved problem.