Added pmproio_getInviteCodes() and pmproio_saveInviteCodes
Added new invite code system and pmproio_checkInviteCode() function
Updated pmproio_getInviteCodes() to return sorted codes if sort_codes flag is true. Updated confirmation page.
Updated Profile page and Account page with new display functions.
Updated version, readme.txt
Merge branch 'master' of https://github.com/messica/pmpro-invite-only into messica-master

Conflicts:
	pmpro-invite-only.php
	readme.txt
Tested up to 4.0