Stemming unknown proper nouns

[meliksahturker]

Hey Olga, good work with zeyrek.

I have a small improvement suggestion. Zeyrek is capable of providing stem of known proper nouns where inflections are attached with apostrophe. Example:
"istanbul'daki" -> "İstanbul"

but merges the inflection with the stem in case of unknown proper noun without parsing the inflections. Example:
"melik'in" -> "melikin"

So my suggestion is it should return the part before apostrophe. I'm not sure about if it should parse the inflection after apostrophe though. I might be missing some other case with apostrophe but here I am pointing out to something with unknown proper nouns and their inflections.

[obulat]

Thank you for opening the first issue here, @meliksahturker :)
Zemberek-nlp has the functionality of parsing unknown words, and I was planning to port it to Zeyrek as well, but didn't have time for it, sorry. I would greatly appreciate any contributions in this area. Other than that, you are free to fork Zeyrek, and just add the 'remove the part after apostrophe' functionality, if you want.