Refactor to use scala.stream.compress.deflate

* Allowed for the removal of GZipper from core
* Simplified the GZip middleware in server

The scalaz.stream deflate doesn't add the GZip header, which is simply prepended for the implementation.
Rename HttpBody to EntityBody.
Overhaul Writable.
Generalize futureWritable to things naturally transformable to Task.
Fix bug in Writable

When encoding a String, UTF-8 was used regardless of the specified charset.
Files are Writable.
InputStreams are Writable.
Paths are Writable.
Change the Process[Task, A] Writable
Readers are Writable.
CharSequences are Writable.
Character and byte ropes are Writable.
Uncomment commented test.
Don't emit unsafe chunks in readerWritable.
Writable[Seq[_]] Considered Harmful.
Remove empty source file.
Add json4s writable support.
Add Argonaut writable support.
http4s-json has no external dependencies and need not be stanadalone.
How did these get here?