Feature/more rules and tests

[ievans]

Add a test suite and a whole bunch of new python rules. New output from make test:

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python/compatibility/python37.yaml
⚠ - python37-compatability-os-module                            TP: 1	TN:0	 FP: 2	 FN: 0
✔ - python37-compatibility-os2-ok2                              TP: 1	TN:0	 FP: 0	 FN: 0
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python/smells/missing-hash-with-eq.yaml
 no checks fired (TODOs: 1)
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python/smells/sleep.yaml
✔ - arbitrary-sleep                                             TP: 3	TN:0	 FP: 0	 FN: 0
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python/exceptions/exceptions.yaml
✔ - raise-not-base-exception                                    TP: 1	TN:0	 FP: 0	 FN: 0 (TODOs: 2)
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python/deadcode/useless-ifelse.yaml
✔ - useless-if-conditional                                      TP: 1	TN:0	 FP: 0	 FN: 0 (TODOs: 1)
✔ - useless-if-body                                             TP: 3	TN:0	 FP: 0	 FN: 0 (TODOs: 1)
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python/deadcode/return.yaml
✔ - return-not-in-function                                      TP: 1	TN:0	 FP: 0	 FN: 0 (TODOs: 2)
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python/deadcode/useless-literal.yaml
 no checks fired (TODOs: 4)
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python/deadcode/useless-innerfunction.yaml
 no checks fired (TODOs: 2)
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python/deadcode/baseclass-attribute-override.yaml
 no checks fired (TODOs: 1)
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python/deadcode/useless-assign.yaml
✔ - useless-assignment-keyed                                    TP: 1	TN:0	 FP: 0	 FN: 0 (TODOs: 2)
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python/deadcode/missing-fstring.yaml
 no checks fired (TODOs: 0)
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python/tempfile/mktemp.yaml
✔ - tempfile-insecure                                           TP: 2	TN:0	 FP: 0	 FN: 0
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python/tempfile/flush.yaml
✔ - tempfile-without-flush                                      TP: 1	TN:0	 FP: 0	 FN: 0 (TODOs: 1)