Removed node_modules and bower_components from gitignore

After doing some reading, the [npm FAQ site](https://www.npmjs.org/doc/faq.html#Should-I-check-my-node_modules-folder-into-git) tells us to checkin the `node_modules` folder if we are building an application. Since this boilerplate is intended for bootstrapping apps, I believe the `node_modules` (and by the same token, `bower_components`) folders shouldn't be present in the `.gitignore`.

Also tweaked the `dist` folder and removed the `public` entry as this causes any folders by these names in `node_modules` or `bower_components` to be ignored too, which we wouldn't want.