Add sanity testing for hAMRonization

[cimendes]

This PR adds, through the pytest package, sanity testing for the parsers implemented so far. This adressed issues #18 and #19.

To run the sanity tests, simple invoke pytest in the test directory. The sanity tests are implemented in the test_sanity.py file, which are automatically detected by pytest. More information is available in the README.md file inside the test directory.
The single-entry files used in the sanity testing are stored in test/dummy. I'm not sure if this is the most appropriate name/location. Raw outputs are available at test/data and contain real reports.

Main issues to be discussed:

• Groot parser: Groot parser implementation #37
• SRST2 parser: Srst2 parser implementation #38

This still to be adressed:

• custom error handling: Add custom error handling #32
• Input file format and structure validation: Input file format and structure validation #39

Additionally, unit tests to each of the parsers functions could be implemented.