0.7.0

CHANGES:

• Numerous minor internal improvements (@polytypic)
• Added many benchmarks to allow better understanding of the overheads of
  composable transactions (@polytypic)
• Exposed shape of _ Loc.t to avoid float array pessimization (@polytypic)
• Made Accumulator automatically scaling and removed optional n_way
  arguments (@polytypic)
• Use polymorphic variant for mode (@polytypic)
• Add ?backoff to Loc.compare_and_set (@polytypic)
• Remove the Op API (@polytypic, @lyrm)
• Fix Hashtbl.clear (@polytypic)
• Fix single location updates to be linearizable (@polytypic)
• Add Xt.compare_and_set (@polytypic)
• Add Dllist.create_node value (@polytypic)
• Workarounds for CSE optimization (@polytypic)
• Changed to use (implicit_transitive_deps false) (@polytypic)
• Move Backoff module to its own backoff package (@lyrm, @polytypic)
• Support padding to avoid false sharing (@polytypic)
• Pass through ?timeoutf to blocking operations on data structures
  (@polytypic)
• Ported to OCaml 4.13 (@polytypic)