added redis strategy
options have been added to the strategies
username based strategy implemented
deterministic percentage implementation
session strategry
added mutators to strategies
Merge branch 'envato_wip' of github.com:envato/flip into envato_wip

Conflicts:
	lib/flip.rb
Merge branch 'envato_wip' of github.com:envato/flip into envato_wip
added a redis store, defaulted datastore backed strategies to redis
added options to session strategy
tidied up includes
fixed derp
inject datatore, use it in UsernameStrategy
Merge branch 'envato_wip' of github.com:envato/flip into envato_wip

Conflicts:
	lib/flip.rb
	lib/flip/username_strategy.rb
symbol or class? iunno what you talkin `bout
deterministic percent refactor
fixed knows
the same set of users wont always be beta testers
specs run again
usernamestrategy specs pass again