Use ShortByteString instead of ByteString

[hasufell]

I don't see a compelling reason to use ByteString. We don't interact with FFI usually when dealing with URIs and we don't have crazy large bytestrings that would make a good argument for them to be pinned.

Similar to FilePaths... ShortByteString is the right decision here as it avoids memory fragmentation. The API has been greatly enhanced as part of the AFPP proposal, so you can use all the functions that ByteString has too: https://hackage.haskell.org/package/bytestring-0.11.3.1/docs/Data-ByteString-Short.html