1.7.4

[1.7.4]

Fixed

• Users will no longer see the message, "Cannot set the submission time of ''
  because it has already been set", when tasks are restarted.
• Bug causing merlin restart to break.

Changed

• Improved internal logic beyond the crude fixes of the prior 2 patches.
• Added a developer cli test for the minimum valid spec format.
• Improvements to the null_spec example, used for measuring overhead in merlin. Includes
  a new null_chain and removes the now-redundant sim_spec.