Document revising up to ports
Make byte-ready?'s port arg optional in sync with R7RS u8-ready?
Document fix
Add read-uvector, rename read-block! to read-uvector!

and also rename write-block to write-uvector.
Rewrite read-bytevector to use read-uvector
Deprecate read-block in favor of read-uvector

Also renamed read-block!/write-block to read-uvector!/write-uvector
throughout the document.
Support r7rs compatible read-string in the core
Finishing doc revision