v0.7 UnitFloor, UnitCeil, and UnitRound

Use "github.com/shopspring/decimal" to make functioins UnitFloor, UnitCeil, and UnitRound.

RandomMapPick

add function "RandomMapPick" to choose one item from a given map.

v0.5: add function ExponentialRandom to generate random number following Ex…

add function ExponentialRandom to generate random number following Exponential Distribution

v0.4

add function "RandomPickN" to pick m indexes from the slice a

v0.2

add function RandomFloat64 to generate float64 in [start,end)

release-0.1

routing algorithms and random functions