VERSION 0.5.2 with Swift 2.3 compatibility

add xtra_int128.swift to Framework-{i,tv}OS

VERSION 0.5.0

improve Lucas-Lehmer Test

rename benchmark/main.swift to benchmark/benchmark.swift; add scripts/

remove POUtil.Prime.tinyPrimes which is no longer needed

cleanup Scratchpad

split tests

switch bigint division from binary-long to Newton-Raphson

normalize PORational(0)