Remove import of qsimcirq from __init__

[thisac]

Removes the import of qsimcirq from the __init__.py file and fixes the tests and entrypoints to import qsimcirq correctly.

This avoids users having to install qsimcirq for the other Cirq devices to work.

[codecov]

Codecov Report

Merging #46 (a11239b) into master (a401c94) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #46      +/-   ##
==========================================
- Coverage   99.07%   99.07%   -0.01%     
==========================================
  Files           8        8              
  Lines         324      323       -1     
==========================================
- Hits          321      320       -1     
  Misses          3        3              

Impacted Files	Coverage Δ
pennylane_cirq/__init__.py	100.00% <ø> (ø)

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[josh146]

@thisac don't forget to also update the changelog! As the number of plugins increases, this becomes more important so as to ensure that we can keep track of changes + when pypi releases are required

[co9olguy]

@josh146 I wonder if we can set up a GitHub action that checks whether there are any updates to CHANGELOG?

[josh146]

Yes! @mariaschuld and I were discussing this recently.

I think the best approach is to have a bot comment a reminder when PRs are opened, rather than have a check that must pass for merging (avoids complexity, and allows for trivial PRs where we don't want to necessarily update the changelog).

See https://github.com/marketplace/actions/changelog-reminder: