Fix #229, #293: Modify parser.py to re-insert quotes correctly

[stephenvincent27]

Passes: parser_test.py parser_fuzz_test.py (?) main_test.py

We are not Python programmers primarily, so do let us know if there are fragments of code that can be rewritten in Python to make it more readable. Other than that, this code conforms faithfully to the flowchart we sent over earlier.

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[stephenvincent27]

@googlebot I signed it!

[dbieber]

Thank you for the PR! I will let you know once I have looked through it more closely.

You mentioned in our discussion on #229 that you had some test cases. Could you add those to this PR?

[stephenvincent27]

Hello @dbieber! Really sorry for the super-long hiatus. I've added relevant tests (some of which we'd discussed earlier), feel free to suggest additions/modifications to them.

[dbieber]

Hello again. Thanks for adding the tests!