Require golang 1.10+ (closes #278)

[abitrolly]

Because strings.Builder was added in 1.10 - https://www.calhoun.io/concatenating-and-building-strings-in-go/

✗ sudo snap refresh go --channel 1.9/stable --classic
go (1.9/stable) 1.9.7 from Michael Hudson-Doyle (mwhudson) refreshed
✗ go version
go version go1.9.7 linux/amd64
✗ GO111MODULE=auto go build
# github.com/wagoodman/dive/runtime/ci
runtime/ci/evaluator.go:137:9: undefined: strings.Builder