Adding `.x` to Travis means use the latest minor version according to its docs.
I didn't update the "Requirements" header because this is just because of Go Modules; see https://github.com/terraform-providers/terraform-provider-google/pull/2932 for why. Since it's just a development change, it doesn't impact _using_ the provider.
Although, out of curiosity- is that header for development? Or is there a real requirement to have Go installed to use Terraform providers?
Pull provider usage docs above building/development, highlight explicitly that upgrading is manual, call out `google-beta` and link provider-versions here too.
PR is against `2.0.0` but I wouldn't hate getting it into master or making `2.0.0` the primary branch on GitHub until we release 2.0.0.
I've seen questions about how to vendor come up from new members of our team and from the community in some OSS issues. Let's make our tribal knowledge a documented process!
Right now, we have a detailed guide to running acceptance tests in [CONTRIBUTING.MD](https://github.com/terraform-providers/terraform-provider-google/blob/master/.github/CONTRIBUTING.md#tests) while this file has the one-size-fits-all guideline of running `make test` and `make testacc` with no arguments. Instead, we can link to the detailed, provider specific guide so that we properly surface the required arguments/environment variables for `make testacc`, and don't incorrectly introduce `make test` as the primary means of testing the Google provider.
With go 1.8, `make build` returns the following error:
```
# github.com/terraform-providers/terraform-provider-google/vendor/github.com/hashicorp/terraform/config
vendor/github.com/hashicorp/terraform/config/testing.go:9: t.Helper undefined (type *testing.T has no field or method Helper)
```
