Use faster version of ed25619 library

[rlittlefield]

A bunch of the ed25519 stuff was dramatically improved for performance with these changes (unsure of original source, might be good to track down for licensing reasons):

https://raw.githubusercontent.com/warner/git-lockup/575b4beae8797fee4c7daa07a5ce0e33667b3c1f/src/ed25519.py

This gives what seems to be a 10x increase in performance for my machine in generating a new monero address using python code.

[rlittlefield]

Another version with the speed improvements can be found here:

https://github.com/warner/python-pure25519/blob/master/misc/djbec.py

[bigreddmachine]

Thanks! I'm definitely aware of these improvements, and have been considering implementing them. Long term, I think the best thing to do will ultimately be using the same C++ libraries as the core Monero code, since they are built to resist timing attacks. But as long as I'm using a python implementation, I might as well use the fastest one, huh?