Improve github build status

[therealbnut]

It would be good to better reflect the build status in github:

• Set the build status to pending when the build is queued, currently it seems to look green (!) until it actually starts running.
• Set the build status to pending when in a wait step, perhaps with a link to continue it, currently it seems to look green (!) until it starts running again.
• If the client times out then set the status to error with an appropriate message rather than failure.

[keithpitt]

Hey @therealbnut! Thanks for the feedback! We shipped the first one last week, so that should work nicely now! I don't think GitHub allows you to add links to commit statuses (they only let you have one link and that's reserved for the link to the build page). With the last one, what do you mean about "client times out"?

[therealbnut]

Ah thanks @keithpitt! I'd been making a wishlist for buildkite for the last 3 or four weeks and finally added them all as issues. Sorry if I've missed any that have been done, and amazing work for beating me to it!

What I meant with times out is that we've occasionally had internet connection issues between our build machine and the build kite servers. In those instances the build's status was set to failed but the script actually succeeded (just without an internet connection). If I'm not misdiagnosing this issue it would be good to keep that status and send it again if the connection resumed, or mark the build as an error ("Client connection lost" or similar) rather than failure.

Thanks for all the work and improvements!