Change import paths to Polymer htmls to use `bower_components` instead of `..`

@devoncarew

Devon, the special treatment of `..` in paths to Polymer elements was required only to support the quirky way Polymer elements themselves are developed. For regular web and Chrome apps we must use the normal path: it's easier to understand, and more importantly the `..` won't work on an actual web server.

Also, I think it's customary to not indent `<head>` and `<body>`.