do not blow up when there is no key
Handle return in parallel threads/processes.
Added test cases for return in threads/processes
Removed incorrect begin/rescue block from test cases
Revert version change (now again 0.6.3)
Use break to exit all threads
Version which should work: Threads can be broken, processes returned.
Fixed type in return message
Use Parallel::Break exception in both threads and processes.
Fix call to correct test case.
break -> nil
document break
v0.6.4
Update Readme.md

Modern progress bar gem's usage, require, and increment signature.
Merge pull request #53 from crazysim/patch-1

Update Readme.md
try to fix travis
Merge branch 'master' of github.com:grosser/parallel
improve readme a bit
Fix small problem in documentation: Do not call ruby-progressbar#finish
because the it is already finished.