Add to splitWith documentation

[Boarders]

The function Data.ByteString.Char8.splitWith lists the following example:

splitWith (=='a') "aabbaca" == ["","","bb","c",""]

I do not understand what the meaning of the ""."" output is whatsoever. I would be happy to improve these docs if someone can explain what is the intended meaning behind this.

[sjakobi]

Does the relationship with intercalate pointed out in the docs for split help clarify?

intercalate [c] . split c == id
split == splitWith . (==)

It might be useful to repeat the intercalate law in the docs for splitWith.

[Boarders]

I think that exactly clarifies things. I'll add it shortly.