Fix bower main to point to lib version

The `main` key in `bower.json` should not point to the distribution version of select.js that includes dependencies (tether) compiled in.

Many asset-pipeline setups directly include the `main` file, so listing *tether* as a dependency along side this would cause redundant code to be included.

I've noticed this issue with all of the tether-based projects and can make a PR on each if this is merged.