This pull request contains a json description file for usage of this repository with comoposer (see http://getcomposer.org/).
Would be very nice if you could add this file, because I am working on a package management solution for Yii 1.1 and yii-bootstrap is an important part of it (Phundament).
Also Composer is very likely to be the package manager for Yii 2.0.
I can understand your point, but let me know if you have an alternative.
Adding the composer.json file to the root of the repo is how composer works, you can have a manual description, but since you've switched to the tag format without a leading 'v' I can eg. require yii-bootrap >= 0.9.12, which would give me all of your future stable releases automatically.
For YiiBootstrap you could require specific versions for Yii, Twitter Bootstrap and yii-less (and there PHPless), which I found very helpful while developing, especially when using different sources like git, hg, svn and zips.
Anyway, just my two cents. I'll setup a bitbucket mirror script to pull your changes and have my composer.json file ;) Edit: This is actually not possible, as a tag can't be modified :(