When deploying a project via the Pulumi.com service, we have to upload
the entire "context" of your project to Pulumi.com. The context of the
program is all files in the directory tree rooted by the `Pulumi.yaml`
file, which will often contain stuff we don't want to upload, but
previously we had no control over what would be updated (and so folks
would do hacky things like delete folders before running `pulumi
update`).
This change adds support for `.pulumiignore` files which should behave
like `.gitignore`. In addition, we were not previously compressing
files when we added them to the zip archive we uploaded and now.
By default, every .pulumiignore file is treated as if it had an
exclusion for `.git/` at the top of the file (users can override this
by adding an explicit `!.git/` to their file) since it is very
unlikely for there to ever be a reason to upload the .git folder to
the service.
Fixespulumi/pulumi-service#122
Instead of doing the logic to see if a type has YAML tags and then
dispatching based on that to use either the direct go-yaml marshaller
or the one that works in terms of JSON tags, let's just say that we
always add YAML tags as well, and use go-yaml directly.
