Added RACSignal Boolean operators from #660

Only accepts a RACTuple of NSNumbers. I was considering considering nil, NSNull and RACUnit as being YES and all other object values as NO, but this seemed really ad hoc.

I've asserted on each of the parameters and used the hand RACSequence operators for enumeration

I've placed the methods next to the ```-not``` method and tried to keep style and indentation the same. I've gone with @kkazuo's idea and @kastiglione's naming