http://pages.github.com << This is the GitHub tool that lets you host websites/pages directly from a GitHub repo.
http://jekyllrb.com/ << Jekyll "Transform your plain text into static websites and blogs."
http://www.slideshare.net/annegentle/git-and-github-for-documentation << hour-long slide deck about using GitHub for documentation
My Jekyll Documentation Theme: https://github.com/tomjohnson1492/documentation-theme-jekyll
Or go to http://idratherbewriting.com and click Jekyll on the top navigation bar.
I've used slack for several clients
https://slack.com/ << Messaging app for teams.
Chatting is chatting, not documentation
If you use the free version of Slack, you can't look back very far
https://enterprise.github.com/home << "The tools developers love, on your servers."
https://opensource.com/business/15/7/continuous-integration-and-continuous-delivery-documentation << Article about CI/CD for docs
I'm working on a DITA project using Perforce, but you could do the same with Git
In translation, as in other pursuits, there is no magic
Please do feel free to email me at annegentle @ justwriteclick.com.
For REST API, see http://www.programmableweb.com/api-research
Here's some API info for you: http://idratherbewriting.com/restapicourse/
one more: https://www.udemy.com/learn-api-technical-writing-2-rest-for-writers/learn/