increment CI go versions from 1.8.x/1.9.x/tip to 1.9.x/1.10.x/tip

[jmank88]

What does this do / why do we need it?

This PR increments the go versions for Travis and AppVeyor. 1.10 is only on release candidate 1, but is expected this month. I don't know if Travis/Gimme will route 1.10.x to 1.10rc1, but in case it does and this turns green: Don't merge until 1.10 is officially released!.

• Changelog
• Simpler appveyor.yml init?

[jmank88]

Travis: I don't have any idea what to do with '1.10.x'. and it fell back to 1.7.4

[jmank88]

Perhaps the end of this script can now change from:
('go list github.com/golang/dep/... ^| find /i /v "/vendor/"')
to:
('go list github.com/golang/dep/...')

[jmank88]

1.10 is out, but still waiting for them to support a.b.x like last cycle: #714 (comment)

Alternatively, we can do "1.10" for now, and change it later.

[jmank88]

Blocked on travis-ci/gimme#130

[ibrasho]

LGTM

[ibrasho]

Can we switch to '1.10' instead of 1.10.x (until travis-ci/gimme#130 is resolved)?

[ibrasho]

What's the difference between '1.10' and 1.10.x? (They should select the same version, no?)

[jmank88]

No difference. Just avoids an extra future PR for a theoretical 1.10.1. Last cycle they fixed 1.9.x quick, so I was holding out, but I'll just change it now.