Unit test fixes accommodating bugfix

* changes to unit-tests/test_functions_PhageTerm_for_multi.test_checkpoint_creation() accommodating that the first read is now considered. e.g. total match length goes from 291333 --> 291441 due to first read length of 108.
* minor restructure of unit tests to include standard setUp() and tearDown() methods, simplifying the creation/deletion of tmp dirs. This means that the unit tests don't fail if they detect leftover tmp directories leftover from a previous run that didn't cleanup because it failed.