Add option for samtools mpileup

Add 0cov region w cov missing test file

Print tsv and vcf version of mutation

The reference property is added for mutations. It is required to be set in
order to print the VCF version of a mutation.

Follow Endle/tvb-library style Travis yaml

Fix #2 Add extra validation columns and tests

This adds the new validation columns as requested by @raylim and adds extra
tests to confirm they are correct. The extra validation columns are useful for
seeing exactly which mutation has been validated. Without it, it is unclear
whether an indel or a snv was validated.

Main script adds extra validation columns. Code refactoring has been done
mainly for readability and more easy testing. The mpileup_parser now only
removes a single character from the quality string. Three new tests have been
added to confirm that both mpileup parser and the construction of the
subsequent extended dataframe are working correctly.

Change packaging based on @hypnek's blog

Change packaging following the blog post by hypnek:

https://hynek.me/articles/sharing-your-labor-of-love-pypi-quick-and-dirty/