Add another baseline fitting algorithm to baseline.py

[Snijderfrey]

I have added a relatively new baseline fitting algorithm I learned to like recently from Applied Optics, 2019, 58, 3913-3920. This might be helpful for others.

[charlesll]

OK thanks, will merge.
I will add it to the examples also and probably release a 0.4.5 version very soon.
Thanks again !

[Snijderfrey]

I might look into other baseline fitting algorithms in the future. If you do not mind, I would include them also into baseline.py and start a pull request. I hope this way is appropriate, I am very new to Github.
I also have some other spectral preprocessing and analysis methods written in Python currently not implemented in rampy. I might find the time to check for compatibility and add them to the corresponding files.

[charlesll]

Yes, please feel free to do so! I'm happy to include new things, for any kind of spectroscopy, as long as it is in the scope of rampy and respects its philosophy.

The best practice is to push such new features and changes on the dev branch, which is 0.4 at the moment, and not the master branch that reflects the current stable version.

I'm looking forward to see your codes :) !