Fixed ARIA attribute name.

Reference:
http://dev.w3.org/html5/markup/aria/aria.html#aria.progressbar
https://developer.mozilla.org/en-US/docs/Accessibility/ARIA/Web_applications_and_ARIA_FAQ#Can_you_show_me_an_example_of_ARIA_in_action.3F
Removed an unnecessary var. See #78
bumped version number
Added an option to control the direction of the circular motion
Merge remote-tracking branch 'upstream/gh-pages' into gh-pages