Update the README.

This makes it easier for first time users by removing the apparent
need to install development things (since vagrant is now in many
disto's repos). Also remove the comment that it's our new server,
since it's been around for quite a while.
Correct the completion message in build.sh

This was upside down, such that it would print "success" on error.
Further changes to make the README easier.

Primarily aimed at new people -- provide some idea of what a 'vagrant
box' is, add the instruction to run the commands in backtick quotes.
Also detect and error about puppet fails.

This is more likely than any other failure, but it's unclear if we
don't error about it upfront.
Even more detail about how to access the VM.

Not everyone knows what NAT means, or how to use the port information.
Provide this via some trivial links and more info about sshing in.
Force-link the localhost links when rendering.

This makes them easily clickable in a browser, thus making it even
easier to browse to the VM's pages.

Change-Id: I79d9d940b5da3c89afab21c884af44debf002799
Merge pull request #6 from PeterJCLaw/master

Update the README.