adding boolean operation tests

The livarot library is incredibly useful, but hard for me to understand. I'd like to try reimplmenting it in Python for use in extensions, but before doing that, it would be helpful to have some test coverage. This is the start of that at a high level, with the intention to write more tests for Shape/PathConversion behavior later.

[==========] Running 7 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 7 tests from PathBoolopTest
[ RUN      ] PathBoolopTest.UnionOutside
[       OK ] PathBoolopTest.UnionOutside (79 ms)
[ RUN      ] PathBoolopTest.UnionOutsideSwap
[       OK ] PathBoolopTest.UnionOutsideSwap (1 ms)
[ RUN      ] PathBoolopTest.UnionInside
[       OK ] PathBoolopTest.UnionInside (1 ms)
[ RUN      ] PathBoolopTest.UnionInsideSwap
[       OK ] PathBoolopTest.UnionInsideSwap (0 ms)
[ RUN      ] PathBoolopTest.IntersectionInside
[       OK ] PathBoolopTest.IntersectionInside (1 ms)
[ RUN      ] PathBoolopTest.DifferenceInside
[       OK ] PathBoolopTest.DifferenceInside (0 ms)
[ RUN      ] PathBoolopTest.DifferenceOutside
[       OK ] PathBoolopTest.DifferenceOutside (0 ms)
[----------] 7 tests from PathBoolopTest (100 ms total)

[----------] Global test environment tear-down
[==========] 7 tests from 1 test suite ran. (104 ms total)
[  PASSED  ] 7 tests.