alpha-270

[] Reader: adds site filter capability to Followed P2s tab page. Now the sites listed in the filters are only those relevant to the page (Following/Followed P2s) [https://github.com//pull/13766]
[] Site Creation: Adds the option to choose between mobile, tablet or desktop thumbnails in the home page design picker when creating a WordPress.com site [https://github.com//pull/13674]
[**] Site Creation: Adds the option to choose between mobile, tablet or desktop home page design previews when creating a WordPress.com site [https://github.com//pull/13673]
[*] Quick Start: Removed the browse theme step and added guidance for reviewing pages and editing your Homepage. [#13855]