* Update CONTRIBUTING.md
- Changed grin support link to keybase grincoin#support channel
- Changed Grin lobby link to keybase grincoin#general channel
- Changed developer channel to keybase grincoin#dev
- Changed @grincoincil twitter account to reddit/grincoin channel for news and developments.
- Added doc.grin.mw link for general grin information.
* edited grin doc link item.
* removed space in a link.
* fixed developers chat channel
* move FAQ.md to https://github.com/mimblewimble/docs/wiki/FAQ and unduplicate (Troubleshooting segment already present on its own wiki page)
* Update doc/style and move it into CONTRIBUTING.
* group up docs overview for more clarity
* link to previously unlinked content in the docs overview
* update + cleanup doc/build
* Update links to reflect troubleshooting is now only in the wiki
* More link fixes and spelling
* Remove doc/usage.md that I've faile to keep updated, and use a wiki page instead
* Last forgotten CONTRIBUTING.md fix