README: https, links, mention Go version, DCO

README.md

@@ -1,6 +1,6 @@
 # Tailscale
 
-http://tailscale.com
+https://tailscale.com
 
 Private WireGuard® networks made easy
 
@@ -9,7 +9,7 @@ Private WireGuard® networks made easy
 This repository contains all the open source Tailscale code.
 It currently includes the Linux client.
 
-The linux client is currently `cmd/relaynode`, but will
+The Linux client is currently `cmd/relaynode`, but will
 soon be replaced by `cmd/tailscaled`.
 
 ## Building
@@ -18,19 +18,31 @@ soon be replaced by `cmd/tailscaled`.
 go install tailscale.com/cmd/tailscale{,d}
 ```
 
+We only support the latest Go release and any Go beta or release
+candidate builds (currently Go 1.13.x or Go 1.14) in module mode. It
+might work in earlier Go vesions or in GOPATH mode, but we're making
+no effort to keep those working.
+
 ## Bugs
 
-Please file any issues on the GitHub issue tracker.
+Please file any issues about this code or the hosted service on
+[the issue tracker](https://github.com/tailscale/tailscale/issues).
 
 ## Contributing
 
-PRs welcome, but we are still working out our contribution process.
-
 `under_construction.gif`
 
+PRs welcome, but we are still working out our contribution process and
+tooling.
+
+We require [Developer Certificate of
+Origin](https://en.wikipedia.org/wiki/Developer_Certificate_of_Origin)
+`Signed-off-by` lines in commits.
+
 ## About Us
 
 We are apenwarr, bradfitz, crawshaw, danderson, dfcarney,
-from Tailscale Inc. You can learn more about us from our website.
+from Tailscale Inc.
+You can learn more about us from [our website](https://tailscale.com).
 
 WireGuard is a registered trademark of Jason A. Donenfeld.