Archive old bootcamps

This was requested by @gvwilson.

Project
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1. Remove all the legacy bootcamp directories from site/bootcamps
   and turn them into GitHub repositories owned by @swcarpentry
   (it'll make the site smaller, a bit, but more importantly it
   will make the build process more uniform).
2. After some time (one month) that a bootcamp end its information
   will be save in some file (`config/bootcamps_saved.yml`) to make
   the build process faster.

Steps
-----

1. Write script to create a repository for each of those
   directories.
2. Incorporate all those new bootcamps' URLs in
   `config/bootcamp_urls.yml` to make sure it's working.
3. Caching old bootcamp info in local file and remove it from
   `config/bootcamp_urls.yml`.

   1. Changes in `bin/get_bootcamp_info.py` to archive
      old bootcamps.
   2. Changes in `Makefile` to be compatible with the new
      feature of `bin/get_bootcamp_info.py`.

Status
------

1. Done
2. Done
3. Done
Add new bootcamps urls
Remove old bootcamps
Cache old bootamps

This close the work started in 886a3b6.