This commit switches from dep to Go 1.12 modules for tracking Pulumi
dependencies. Rather than _building_ using Go modules, we instead use the `go
mod vendor` command to populate a vendor tree in the same way as `dep ensure`
was previously doing.
In order to prevent checksum mismatches, it was necessary to also update CI to
use Go 1.12 instead of 1.11 - which also necessitated fixing some linting errors
which appeared with the upgraded golangci-lint for 1.12.
Instead of duplicating information about how to build Pulumi from
source in both `README.md` and `CONTRIBUTING.md`, just have the
`README.md` point at `CONTRIBUTING.md`.
Fixes#2197
We run the same suite of changes that we did on gometalinter. This
ended up catching a few new issues, some of which were addressed and
some of which were baselined.
- Remove the forked copy of the toolset
- Stop installing `pipenv` in sdk/python/Makefile
After this, we'll require that you already have `pipenv` present
before building.
