Upgrade to Docpad v6.69

Most importantly, custom version of Primus is used in favor of Socket.io,
live reloads work very stable, however not as immediate as I would wish (this
doesn't seem like issue of Primus though).

Also, upgraded to `docpad-plugin-bowermount` v2.4.6 which works great with
current version of Docpad (v6.69).

Added some more JS modules and blog posts with rootet URIs to see better
picture of how all these assets play together.