Fix travis builds

[Oscil8]

Old versions of Go are no longer supported by errcheck. It is documented as requiring Go 1.9.

Oddly, I am seeing builds failing on Go 1.9 and 1.10 but succeeding on 1.11 and newer. The build errors for 1.10 are:

0.02s$ make errcheck
errcheck ./...
error: failed to check packages: unsupported version of go: exit status 2: flag provided but not defined: -compiled
usage: list [-e] [-f format] [-json] [build flags] [packages]
Run 'go help list' for details.
make: *** [errcheck] Error 2
The command "make errcheck" exited with 2.

and for go 1.9 it lists usage information for the go list tool rather than just suggesting details.

[Oscil8]

Interesting; no idea why the builds against the pull request are failing but the same commits build in Travis on my branch: https://travis-ci.org/Oscil8/kazoo-go/builds

[Oscil8]

I filed an upstream bug on errcheck about support for 1.9, 1.10 which seems to have been broken recently: https://github.com/kisielk/errcheck/issues/167