Add doctest to .travis.yml (#1824)
Add doctest to .travis.yml (#1824)

* Add doctest to .travis.yml

Was supposed to be in a previous PR, but appears to have been lost in a merge conflict with the removal of the perf tests.

* Update .travis.yml

balopat/Cirq,quantumlib/Cirq,balopat/Cirq,balopat/Cirq,quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq,quantumlib/Cirq