Use Number instead of Int for `read`

[matthewleon]

I've made a branch here to show this in a test: https://github.com/matthewleon/purescript-node-buffer/tree/uint32-test

Relevant code:

testUInt32 :: Test
testUInt32 = do
  buf <- fromArray [-1, -1, -1, -1]
  readVal <- read UInt32LE 0 buf
  logShow readVal -- 4294967295
  logShow $ readVal - 1 -- -2
  -- chaos reigns: try to uncomment the line below
  --logShow $ readVal == 4294967295

Purescript Ints really don't play nice with these operations. They probably require something like https://github.com/zaquest/purescript-uint

[hdgarrood]

Yes, we should have these functions use a UInt type. I'd rather it be in contrib if we're going to depend on it in this library, though.

[matthewleon]

Makes sense. I'd be happy to see it make its way into contrib.

[hdgarrood]

Come to think of it, we really ought to be using Number as the return type of read, since you can read a Double{BE,LE} or a Float{BE,LE} out of a Buffer, and clearly any integer type is unsuitable for that. Using Number as the return type addresses the UInt32 issue too. Since these libraries are meant to be low-level bindings, I think the loss of convenience is acceptable.