Added element visibility check before calling _show_element function on element

Line 28, added a check to see if the element was currently visible on the page. If Not Visible don't show element
fix "Type mismatch" error in IE8
only show overlay on visible elements
supporto touch chardinjs
Merge pull request #43 from yeaha/patch-2

Only show overlay on visible elements
Compile with new additions from recent PRs.
Merging recent changes by heelhook
Merged touch support change by izifortune
Merged visibility check from sweetog
Merged IE8 type mismatch fix from yeaha