Add README.md and CONTRIBUTING.md, refs #17189
Refs #17214.  Add check for for max==min to dijit Slider, and added automated tests.
update CSS so arrow doesn't show on toggleable=false Fieldset
fix text selection problem on IE9 in quirks mode, fixes #17216
thanks to neek for the investigation and patch
(cherry picked from commit c86c4ea8504875fa749fc096043907bdf90de1e5)
Fixes #17217.  Forward port [2876164aa20aff71392d37d3d492e30d4618c6b3/dijit] to trunk.
Fixes #17154.  Call stopPropagation() for keypress events to prevent parent widget's from stopping the events.