Some robustification of bad agent/user/league ids.

Won't crash server, but also does not redirect.
Front-end modification of alpha/beta added.
Backend saving + form validation of league alpha, beta, n
Redistribution modified with new rules.
Switched bid and ask for buy/sell (bug--were backwards)
Added league default values on creation.

Creation synced to edit as well.
Rewrote the login system to check/display messages.
Registration re-written with failure messages.
Editing profile doesn't allow duplicate email/username.
League: unimplemented options hidden
Password verification added.
readme: installation and back-end trading instructions added
Navigation enhancements.
Bug fixes of league navigation buttons.
Save profile redirect fix.
Upgraded agent descriptions.
Backend tracking of historical values
Historical query added to readme.
Trading now works with HTTP GET.

Readme updated with instructions.
Merge branch 'robustification'

Conflicts:
	README.md
	public/js/controllers/users.js
	public/views/users/profile.html