rubico/monad/Stack

## Stack
the stack data structure

## synopsis
```coffeescript
new Stack(values Iterable|any) -> Stack {
map: function,
concat: function,
chain: function,
push: function,
pop: function,
top: function,
}
```

## description
A **Stack** is a data structure that supports `push` and `pop` operations in O(1) time as well as monadic operations that enable iteration, concatenation, and flattening. Items pushed onto a stack are first in last out (FILO).

```javascript [playground]
const myStack = new Stack([1, 2, 3])

console.log(myStack) // Stack [1, 2, 3]

myStack.push(4)
myStack.push(5)
myStack.push(6)

console.log(myStack) // Stack [1, 2, 3, 4, 5, 6]

console.log(myStack.pop()) // 6
```