Ignore proxy pages during building

[ascendbruce]

connects to #2

Why is this change necessary?

• Get errors when middleman build

undefined local variable or method `country' for
#<#<Class:0x007ff791497d58>:0x007ff79177c348>
/Users/bruce/Projects/taiwanese-work.in/source/country_template.html.erb
:1:in `block in singleton class'

How does it address the issue?

• Add ignore option in proxy config.

In most cases, you will not want to generate the template itself without the person_name variable, so you can tell Middleman to ignore it https://middlemanapp.com/advanced/dynamic_pages/