Modelmatcher

* Last version should have increased the minor version number (because of new feature), so bumping
that number now instead.
* It is no longer an error to request more samples than there sequence pairs. It is just limited to
the number of available pairs.
* Sampling information is now added to JSON output.

* Added --version
* Corrected MrBayes model names
* Implemented the --sample-size option, to offer a limit to the number of sequence pairs that are
consider, and avoid a O(n^2L) trap in favor of O(L) behaviour.
* Started using SonarCloud.com
* Improved setup.py
* Changed identifiers to follow PEP-8
* A first unit test has been implemented.

* Getting the package to work as useful module as well.
* Tried to make important functions and classes available after "import modelmatcher",
without knowing the actual files". So, avoiding
"from modelmatcher.models import RateMatrix"
and instead allowing "from modelmatcher import RateMatrix".
* First tiny attempt of getting unit tests running.
* Ensured that, when outputting for IQTREE, only models known to IQTREE are considered.

Version got messed up.

* Added more models:
- mtDeu
- mtInv
- mtMet
- mtPro
- mtVer
- PMB

* Added support for testing MSA amino-acid frequencies on top of the
model-specified probabilities, as suggested by Ingo Ebersberger.
* More output formats.