[fix-hang] Specify most recent non-blocking version of guard
[fix-hang] CHANGELOG and GEMSPEC
v0.5.1. See CHANGELOG.md for details.

* fix-hang:
  [fix-hang] CHANGELOG and GEMSPEC
  [fix-hang] Specify most recent non-blocking version of guard
Bringing in 0.5.1 fix to upcoming

Merge remote-tracking branch 'origin/master' into upcoming