#88 Built-in binomial coefficients

[Martin Büttner]

Those aren't too hard to implement yourself with factorial, but a) the factorial implementation is a bit ridiculous (compared to swapping the second operand to the lower half and then alternating between multiplication and division) and b) it's a very useful function for all sorts of combinatorial applications, so it would probably deserve a 2-byte operator.

Oh, look mB is still unused. :)

[Martin Büttner]

I just noticed, from a golfing perspective, the current situation is quite insane. The shortest way to get the binomial I can find is S*\Te[e!, which is kinda impractical. :D