Fix 228 - Use bower to fetch app externals

Fixes #228
Ah! Got it now. Thanks.

Before proceeding, let me emphasize those templates we're talking about are server-side templates. So, all these if-else-s never "escape" to the client-side this way. But, they are processed and their output are served to the client.

Moving on... You suggestion is a working alternative. We could change the code to reflect it. Although, note we'd have to create a bunch of other variables to reflect other paths. Note how different the source for JSes are below. In production, JS files are concatenated. In development, they are not. So, it's not only a matter of path. Therefore, I question whether this alternative would simplify or even add more complexity to the templates.