twbs/bootstrap — pull request #13502 by printercu (2014-05-04 10:29:40+00:00)
Title: Variables for media queries

This allows use media queries like this:
```less
@media @sm-only {
}
@media @md-up {
}
```
It also adds `screen` for all current media queries. I can remove it, if you think it's not necessary.