Create test cases for validating start and end polygons in a spec

[singhish]

As discussed during our morning standup meeting, testing the function check_start_end_contains in Validate_spec_before_upload (https://github.com/MobilityNet/mobilitynet-analysis-scripts/blob/master/spec_creation/Validate_spec_before_upload.ipynb) is tough due to how complex it is (compared to, for instance, testing the checking of overlapping time ranges).

@shankari has agreed to address this particular issue. One of me or @shankari will get around to this issue.

[shankari]

well, we agreed that we would file the issue, and see which of us got to it 😄 first

[singhish]

whoops, my mistake -- forgot about that, sorry!