Expose C++ arrays to Python without data copying

[nquesada]

Now the returns of the hermite functions are not copied but are passed transparently into numpy arrays

[codecov]

Codecov Report

Merging #123 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #123   +/-   ##
=======================================
  Coverage   97.72%   97.72%           
=======================================
  Files          12       12           
  Lines         881      881           
=======================================
  Hits          861      861           
  Misses         20       20

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e13a0d6...6c74ccb. Read the comment docs.

[nquesada]

This is a benchmarking of the operations in thewalrus.fock_tensor vs the operations in fock.ops in strawberryfields:

[nquesada]

Wonder if it is worth precomputing the first 50 or so square roots of integers and not have to calculate them on the go.

[trevor-vincent]

Thanks Nico, I flagged a couple of possible optimizations. Let me know what you think.

[josh146]

Really nice :)