Remove Nasty bits from Pair

[evilsoft]

So, back when Pair was creates some horrible things were done, just to get that darn of.
Some cruft needs to be cut from Pair:

• Remove of
• Remove value
• Add toArray
• add pairToArray transformation
• add pairToList transformation

EDIT: After some long, hard thought on this, decided to keep the Semigroup constraint for ap, chain and concat. They do in fact provide much value for things like a cheap Writer (which is just a Product type with a Semigroup in its fst.

[evilsoft]

Okay so after starting this change, turns out I will not be adding pairToArray and pairToList and will not add toArray to the Pair. While it is valid in JS, by allowing to move from Pair to Array or List, then we lose some of the benefits of having a List/Array of a single type.

since there will be special handling anyway, it makes sense to let the user use merge to make it a one "action" thing to map and extract into a value they have control over. For example, if they want to create an array like [ fst, snd ], then they can easily do things like this:

const { Pair, merge, reverseApply: thrush } = crocks

const f =
  thrush(Pair('George', 5))

// { name: 'George', count: 5 }
const obj = 
  f(merge((x, y) => ({ name: x, count: y })))

// [ 5, 'George' ]
const arr =
  f(merge((x, y) => [ y, x ]))

This seems like the more powerful interface

[evilsoft]

Merged PR#86.
In master and going out with 0.4.0.
Closing!