Tests for sequencing_error_model.rs

[joshfactorial]

The code for sequencing error model (common/src/models/sequencing_error_model.rs) compiles, but there are no tests in place to test any of the functionality. Tests of functionality. I added an example rng generator into the test. Would like 100% coverage for this one, if possible, because it is an important core feature. If testing reveals any issues, that will be helpful to know.