0.5.0

CHANGES:

• Optimized Michael-Scott queue with a safe and an unsafe versions (@lyrm,
  @polytypic)
• Optimize spsc queue : unsafe optimizations (@lyrm, @polytypic)
• Optimize spsc queue : optimizations without Obj.magic (@lyrm, @polytypic)
• Tweak treiber stack (@polytypic)
• Disable implicit transitive dependencies (@polytypic)
• Fix dune rules to specify package (@polytypic)
• Lock free skiplist with size (@polytypic, @lyrm, @sooraj-srini)
• Wait-free size for lock free data structures (@polytypic, @lyrm, @nikochiko)