Move skipSpace from value callsite to inside the definitions of value and value'

A three-liner for addressing: https://github.com/bos/aeson/issues/215#issuecomment-52565616

I tested this with the following file:

    module Main where
    
    import Data.Text
    import Control.Lens
    import Data.Aeson.Lens
    
    main = print $ (pack " {}") ^?! _Object

I don't know the Haskell testing frameworks well enough to add the test to the project. If anyone could give me some basic direction on the matter, I would add them.