[PATCH] docs: Update deployment installation guide for v2.1

[Stephen Finucane]

On Sat, 2018-06-02 at 21:55 +0100, Stephen Finucane wrote:
> There are no actual changes needed from the Patchwork side so this is
> mostly a cleanup.
> 
> - Use Ubuntu 18.04 (including package names)
> - Resolve some minor issues with commands
> - Remove use of "trust" authentication for PostgreSQL
> - Minor style changes
> 
> Signed-off-by: Stephen Finucane <stephen at that.guru>

I ran through this again earlier in the weekend and it worked without
issues. We're also testing this somewhat through the use of Ubuntu
18.04 in the docker setup. As a result, I've gone ahead and merged
this.

Cheers,
Stephen