Remove `dist/firepad.min.js` from bower.json's `main` array.

Having both the regular and the minified version of the JS file in `main` leads to inclusion of both in the HTML file when a build tool like [grunt-bower-install](https://github.com/stephenplusplus/grunt-bower-install) is used. In addition to that, the filename of the minified version is `dist/firepad-min.js` and not `dist/firepad.min.js`.