Improves support for Composer and Labrador and LabradorGuide

- Cleans up the /bin/labrador-skeleton.sh command to be less duplicative
  and to only copy up over directories and files that are required for
  out-of-the-box Labrador to show the appropriate welcome page and guide

- Changes LabradorGuide services register to be more consister with
  other service registers and to fix the ambiguity of the template
  directory based on whether the user installed via Composer or just
  cloned the repo directly.

- Adds some default CSS & JS files and moves some of those files out of
  the labrador_guide subdirectory and directly into /public root.

- Fixes CI servers to ensure they're using an updated version of
  Composer

- Begin some README cleanup