Merge branch 'release/1.6.7' into develop

* release/1.6.7:
  Increment release number to 1.6.7
Add Mersenne Twister
Update zt_uuid to use zt_random
Increment version number to 1.6.8
Merge branch 'release/1.6.8'

* release/1.6.8:
  Increment version number to 1.6.8
  Update zt_uuid to use zt_random
  Add Mersenne Twister