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

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.)
Merge pull request #570 from gvwilson/make-instructors-more-prominent

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