When you use Visual studio express (or above) and go to Manage Nuget package for this solution then you see it’s show you the new version you want to install. Till now 3.x has been released.
If you want to use old 2.3.2 version then look at this https://www.nuget.org/packages/Twitter.Bootstrap/2.3.2
Run this in package manager console
Install-Package Twitter.Bootstrap -Version 2.3.2
This will add the old version of bootstrap (which version you have tried) you want in your project.