Added Logic lecture

I would appreciate comments and criticism! 
I think it may be worth clarifying what R does in this situation. Since the left operand is a vector of length 1 and the right operand is a logical vector of length 3, R "recycles" the left operand to create a vector of the same length as the right operand. In other words, R actually carries out `c(TRUE, TRUE, TRUE) & c(TRUE, FALSE, FALSE)`. Then the result comes from comparing the two vectors element-by-element. First two elements, then the second two, then the third two.