community standards

[StefanKarpinski]

Here's a community standards document:

http:https://julialang.org/community/standards/

The remaining issue is where and how to link to it from.

[ViralBShah]

How about link it in the community section and also in CONTRIBUTING.md?

[StefanKarpinski]

Those both seems like good places. Feel free to add if you want or I'll do it later.