Use Bower to track dependencies

[.bowerrc](.bowerrc) configures the directory for bower to install
dependencies, in this case `app/scripts/vendor`. Bower will create that
directory upon calling `$ bower install` from the project root.

Since we are now using bower to install dependencies _including_
requirejs, we must update the path to require.js, to its new home in
the vendor folder. This path is adjusted in the `<script>` tag in
[index.html](app/index.html).

The path to `jquery` is also updated in [app.js](app/app.js).

Finally, the `paths` config in [component.json](component.json) is updated so that `jquery`
points to new install location from bower.