Updated api docs for yank/unyank.
Updated api docs for yank/unyank.

1337807/rubygems.org,bpm/getbpm.org,square/rubygems.org,square/rubygems.org,rubygems/rubygems.org-backup,bpm/getbpm.org,rubygems/rubygems.org-backup,dstrctrng/private_event,1337807/rubygems.org,dstrctrng/private_event,square/rubygems.org,rubygems/rubygems.org-backup,1337807/rubygems.org