Removed unused rules + minor cosmetics
Updated version number to 1.8.0
Rules for the "Today" button + minor cosmetics
Updated jQuery version from 1.9.1 to 1.10.1
Fixes, additions and changes

- fixed a bug where deciding whether the "next" and "previous" buttons
should be shown, the script was not always working as expected; thanks
<strong>jojo</strong>;
- fixed a bug where the date picker was not working in IE8 and below;
thanks <strong>sascha</strong> and <strong>Souli</strong> for reporting;
- added a new property called "show_select_today" which, when set to
TRUE, allows for quick selection of the current date; thanks
<strong>Matt Coady</strong>;
- changed the name of the "always_show_clear" property to
"show_clear_date" and it now can be true, false or 0 (zero), instead of
just true or false
- changed the caption of the "clear date" button from "Clear" to "Clear
date";
- minor optimizations in the code;