To convert bootstrap 3 to RTL you can use https://github.com/ded/R2
but be aware that there is currently a pending issue with media queries not being converted properly.
If you can't wait for this to be resolved by the maintainer you can manually patch the
rs.2js based on my branch at https://github.com/ded/R2/pull/23/files
Note that this is not thoroughly tested and will probably not be maintained if I won't have time to maintain it.
EDIT: The above issue is now merged into the R2 master and also have been tested quite well.
If you want a rather stable, working, version of RTL bootstrap.css you can use the one from my repository at https://bitbucket.org/levynir/bootstrap3-rtl. Even if you decide to brew your own version, I recommend that you read the README on this bitbucket as there are some caveats to RTLing bootstrap.