Updated trigfind to use ligo-segments and lalsuite, not glue

[duncanmmacleod]

This PR updates the trigfind package to use ligo.segments and lalsuite, and removes all references to lscsoft-glue.

I also reworked the test suite using pytest to make it more readable.

[coveralls]

Pull Request Test Coverage Report for Build 61

• 111 of 118 (94.07%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.0%) to 97.665%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
trigfind/test_trigfind.py	102	105	97.14%
trigfind/core.py	9	13	69.23%
<!--	Total:	111	118	94.07%	-->

Totals
Change from base Build 58:	-1.0%
Covered Lines:	251
Relevant Lines:	257

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💛 - Coveralls