0.5.0

CHANGES:

• Fix regression from 6379b47 (server-sig-algs should be Hostkey.preferred_algs)
  (#75, @reynir)
• Avoid functors over Mirage_time.S and Mirage_clock.MCLOCK (#76 @hannesm)
• Adapt to mirage-crypto-rng 1.2.0 (#76 @hannesm)