Add the new breakpoint betweeen 480px and 768px

[aagouda]

I am suggesting to add the long discussioned topic on bootstrap website about this breakpoint.

Here is the CSS code for it, at least you can add it as a separate files as it is:

The original CSS code for this here:

https://gist.github.com/firepol/7942411

But it is missing some class for visibility and fixes, I did all and upload it here:

https://gist.github.com/mewsoft/91ff69da8996f81ca830

I also did the RTL version from this CSS in the file bootstrap_ms_rtl.css:

https://gist.github.com/mewsoft/91ff69da8996f81ca830#file-bootstrap_ms_rtl-css

Topics for this are here:

https://github.com/twbs/bootstrap/issues/10203

I run to the real need to this range because the 768px is too large for Mobiles, until soon desktops were 640px. I hope you consider this. Thanks for your excellent effort.