Modifying default layout of bootcamp pages to give instructors and helpers more prominence.

[gvwilson]

1. Moved list of instructors from index.html to _layout/bootcamps.html in order to put it in the header.
2. Added a dependency in Makefile so that the site will rebuild when templates are changed.

Question: should the entire header well be moved into ./index.html so that it's easier for bootcamp site authors to find and modify? (We've found in the past that people find the _includes mechanism confusing.)