Mailmap from boot camps repo

Requested by @gvwilson in #287.

The previous two commits came from swcarpentry/boot-camps#9 and swcarpentry/boot-camps#24.  This adds entries for other authors, as far as I could determine from searching the GitHub and the wider net.  Before this gets merged, it would be nice to get confirmations from the folks I've mapped (@cavestruz, @ChristinaK, @lexnederbragt, @mattphotonman, @mollygibson, @sckott, @tshauck, and @HaveF) that this is the name they want us to use.  I couldn't find a GitHub account for Steve Haddock, but I'm pretty sure I [have that mapping right][1] ;).

[1]: http://www.mbari.org/staff/haddock/