Write module to parse `dnadiff` output

[kiepczi]

After developing the initial workflow for the dnadiff method #12, we need to ensure that we can reproduce the AlignedBases value provided by dnadiff.

To achieve this, we should:

• Write a module to parse all files generated by the Snakemake workflows for the dnadiff method.
• Generate a test set of expected output using dnadiff.
• Use pytest to compare the expected output with the output provided by the module.

[kiepczi]

I started working on this under the issue_17 branch.

So far, I have written functions to parse .mcoords and .rdiff files. The code still requires testing and few tweaks.