Adding mammal ecology data for teaching SQL

This is a simplified version of:
http://www.esapubs.org/archive/ecol/E090/118/default.htm

It was been successfully for teaching SQL to ecologists
and evolutionary biologists at  three bootcamps so far.

Both the raw datafiles and a pre-assembled SQLite database
are provided to allow for different starting points.
Merge pull request #30 from ethanwhite/master

Adding mammal data used to teaching SQL