Log Message:
Update to 0.7.4:

v0.7.4:
 - Fixing a bug about dangling processes, in case of using "ts -r".
v0.7.3:
 - Add option '-N' to set the number of slots required for a job to run.
   Proposed by Sergey Litvinov.
v0.7.2:
 - Add option '-E', to keep stderr apart. It goes to "`ts -o`.e".
v0.7.1:
 - Implement check of ownership of the socket. Security bugfix.