v0.6

v0.6 2018-07-05 Paris (France)

• breaking change API:
  From a consensus between people who use digestif, we decide to delete *.Bytes.* and *.Bigstring.* sub-modules.
  We replace it by feed_{bytes,string,bigstring} (digest_, and hmac_ too)
• breaking change semantic: streaming and referentially transparent
  Add feedi_{bytes,string,bigstring}, digesti_{bytes,string,bigstring} and hmaci_{bytes,string,bigstring}
  (@hannesm, @cfcs)
• Constant time for eq/neq functions
  (@cfcs)
• breaking change semantic on compare and unsafe_compare:
  compare is not a lexicographical comparison function (rename to unsafe_compare)
  (@cfcs)
• Add consistent_of_hex (@hannesm, @cfcs)