Initial commit of basic number theory functions.

All of these are untested and probably don't work, but have general concepts.
Broken lcm/gcd with main for testing
Reorganize

Separate numbth.o into prototypes and definitions. Use implicit rules in
makefile.
Remove wayward cout
Use vector's back method
Use auto for range based loops. Like a boss
Use initializer lists for vectors
Merge pull request #1 from silverhammermba/reorg

Reorg