Add Contributing page

[solnic]

Would be great to have a dedicated section where we document info about contributing

Things I'd like to see in this section (random order):

• Info about writing tests
• Info about CodeClimate and how we use metrics
• Info about versioning scheme
• Info about issues, labels and how to find a task to work on
• A CoC or a statement that we have a CoC and a link to it
• A list of current contributors
• ???

Makes sense? WDYT?

[timriley]

All of this sounds really good to me. I think it'll make the organization a lot more "tangible" and approachable. I like the idea of recognising current contributors too.

Some other content ideas:

• Info about what makes a good library, and any philosophy around the kind of API they should offer
• A note on how we collaborate (github issues + gitter)

I've got the feeling we might need a secondary nav area in our layout for linking to pages like this. Perhaps something in the footer? Alternatively, we could have a top level "About" page which has its own side menu like the gem pages.

[AMHOL]

@solnic didn't someone do something with ROM to automatically generate a list of contributors from the github API or something?

[solnic]

@AMHOL yes, @hmadison did