/cc @rgarcia Should just pass it in as a param

/cc @rgarcia

/cc @rgarcia - "Message" in Ui is the non-bold colored messages and
are meant for sub-messages or steps part of a larger message. "Say"
is used for the bold stuff. This is more in line wit how Packer works.

/cc @rgarcia - Not sure why this was capitalized to begin with

/cc @rgarcia - Since you opened the pull request, common config
decoding stuff has been pulled out into the common Package. This
simplifies a lot of code.

/cc @rgarcia - This just forces the tests to make sure the package
even builds. Better than nothing.

/cc @rgarcia - I don't know of any Go packages that follow this naming
convention so I just lowercased it.

provisioner/salt-masterless: masterless salt provisioner

We shouldn't need a different one for each driver ...

Conflicts:
	builder/vmware/driver_workstation9.go

We have two choices for VMware on Linux.  We already support
Workstation, add support for Player too.

VMware Player doesn't come with vmware-vdiskmanager, so fall back to
using qemu-img if we can find that.

Conflicts:
	builder/vmware/driver.go

builder/amazon/common: handle missing source AMI error

Specifying a non-existent source AMI will result in an empty array of
images in the response which would cause an "index out of range" panic.
This change handles this case more gracefully with an error message.

/cc @rasa - This is more idiomatic Go: to share the platform-independent
stuff and make the platform-specific stuff unexported functions