Document that .progress-bar-striped doesn't work in IE<=9; fixes 16058
Document that .progress-bar-striped doesn't work in IE<=9; fixes 16058

BS3 commits: f3ae9430f271c0cd8e15942d5c1ded6a0ea181e9

up2vs/todc-bootstrap,aaroncnhk/todc-bootstrap,todc/todc-bootstrap,2947721120/todc-bootstrap,mozillo/todc-bootstrap,2947721120/googlebt4,ztx1491/todc-bootstrap,todc/todc-bootstrap,todc/todc-bootstrap