use quotes around all element attr vals in JS; fixes #12946
switch to grunt-css-flip for RTL CSS generation
Disable requireCamelCaseOrUpperCaseIdentifiers JSCS option completely, for now

Can't disable it just for the Gruntfile due to https://github.com/mdevils/node-jscs/issues/287
Merge pull request #12949 from twbs/use-our-grunt-plugin

switch to grunt-css-flip for RTL CSS generation
re-enable requireCamelCaseOrUpperCaseIdentifiers in JSCS & use `null` to override it for Gruntfile
Merge pull request #12950 from twbs/jscs-null-trick

re-enable requireCamelCaseOrUpperCaseIdentifiers in JSCS
Merge pull request #12948 from twbs/js-quote-attr-vals

use quotes around all element attribute values in JS
add docs page listing relevant outstanding browser bugs
add link from Getting Started page to Wall of Browser Bugs page
Merge pull request #12943 from twbs/browser-bugs

add Wall of Browser Bugs docs page
Merge remote-tracking branch 'upstream/master'