Fix Composer version check

I've seen this for a few versions of VVV that in both Ubuntu 12.04 and 14.04 the below line of code would always evaluate to false, and as such, always install Composer instead of checking for an update:
```bash
if [[ -n "$(composer --version | grep -q 'Composer version')" ]]; then
```

I propose using the following, which seems to evaluate more consistently:
```bash
if [[ -n "$(composer --version --no-ansi | grep 'Composer version')" ]]; then
```
Fix typo concerning paths
Fix typo in file path.
Update phpunit, mockery and boris composer packages
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
Instruct Curl to follow 302 redirect for Wordpress source files
Merge pull request #450 from jmbarlow/curl-fix

Instruct Curl to follow 302 redirect for WordPress source files
Use HTTPS when downloading the latest WordPress package

See #350

"libcurl performs peer SSL certificate verification by default"
http://curl.haxx.se/docs/sslcerts.html

This is better practice and eliminates the current redirect from
HTTP to HTTPS. We'll leave the `-L` flag, as future redirects are
possible.

Thanks @nacin
Merge pull request #452 from Varying-Vagrant-Vagrants/https-wp

Use HTTPS when downloading the latest WordPress package
Add a license file - MIT

Per discussion in GitHub issue #346, we're applying the MIT license
to the VVV project, copyright the contributors of the VVV project.
Make note of MIT license in the VVV Contributing document
Add copyright / license note to README
Merge pull request #421 from nacin/patch-1

Fix typo in file path
Merge pull request #400 from thewebists/patch-1

Fix Composer version check
Merge pull request #418 from iparr/master

Fix typo concerning paths
Update the list of contributors
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 #431 from GaryJones/update-composer-packages

Update phpunit, mockery and boris composer packages
Merge pull request #453 from Varying-Vagrant-Vagrants/new/license

Apply the MIT License to VVV

So happy.

Fixes #346
Merge pull request #462 from Varying-Vagrant-Vagrants/nginx-mainline

Install the mainline version of Nginx