Add wildcard Nginx rules to load default VVV domains via xip.io

local.wordpress.*.xip.io
local.wordpress-trunk.*.xip.io
src.wordpress-develop.*.xip.io
build.wordpress-develop.*.xip.io
where * represents an IP address

The goal of these rules is to allow other devices on your network to
load these websites using URLs like the following
local.wordpress.192.168.1.10.xip.io
local.wordpress.10.0.1.20.xip.io

See #263
Install the mainline version of Nginx

In the world of Nginx, mainline can be considered the most feature
rich and the most stable. The "stable" release receives only bug
updates. A good explanation of this was posted by the nginx project
after the initial 1.7.x release from 1.6.x

http://nginx.com/blog/nginx-1-6-1-7-released/

I've used nginx 1.7.x in production since that day and have not had
any troubles. I think we should be good to move to mainline as our
default provisioning.
Merge pull request #462 from Varying-Vagrant-Vagrants/nginx-mainline

Install the mainline version of Nginx
Merge pull request #449 from salcode/nginx-xip-io-rules

Add wildcard Nginx rules to load default VVV domains via xip.io
add calibrefx provision for development environment
update readme