note specific versions of IE where progress bar animation supported; fixes #12437
rm outdated note about lack of .col-{xs,sm}-offset-0; fixes #12439
Allow the bootstrap package in npm to expose css

Many modules in npm are starting to expose their css entry files in their `package.json` files. This allows tools like `npm-css`, `rework-npm`, and `npm-less` to import bootstrap from the node_modules directory.
Merge branch 'patch-1' of github.com:Techwraith/bootstrap into patch-1