fix call
add iterate and replicate functions
fix docs
fix argument order
fix pi, make it a function
fix product
match Haskell behaviour more closely

* min/max return first/second arg when equal
* round 0.5 towards even, rather than up
* words splits on \s+, ignores leading/trailing whitespace
add some math functions
add some array functions
add some string functions
add const_ function
add 'tuple' and currying functions
rebuild readme
add tests