Swap content at docs.filecoin.io

[terichadbourne]

• Add an additional subdomain go.filecoin.io pointing to the old docs site (just the tutorial portion currently hosted at docs.filecoin.io/go-filecoin-tutorial (generated by https://github.com/filecoin-project/docs) - removing the trailing /go-filecoin-tutorial/ following it). (The contents of the landing page at docs.filecoin.io will no longer be needed.)
• Update docs/.vuepress/public/_redirects in new docs site to lead to new go.filecoin.io location for that tutorial (see PR ON HOLD: Update redirect URL for go-filecoin-tutorial #56)
• Cutover docs.filecoin.io domain to display the new docs site, currently hosted at filecoin-docs.netlify.app and generated by VuePress at https://github.com/filecoin-project/filecoin-docs
• Update new site docs/.vupress/config.js to reflect correct base URL (see PR ON HOLD: Update domain in config #57)
• Update root content of the old doc site to remove any old data or broken links

Files in new site that will need edits as part of this process: