fixed typos/language in CONTRIBUTING.md

I studied the naming convention part of the contributing (to remind me of how we name) and found it in parts not really readable and a bit too scetchy, or even too strong in language.

Since it is kind of an official document, i thought it could take a brief rework. I didnt change any thing semantically, but sometimes did make some changes to wording and sentence structure. I think the content will be taken much more seriously, if formulated in officiall/technical sentences (as opposed by a colloquial remark style), so i hope changes dont change any content and just improve the text.