Add a download-URL base fact
Add a custom loader for boxen facts
Merge pull request #114 from boxen/download-base-url

Add a boxen "base download url" for binary downloads
Ensure boxen::config facts' are lazy

Avoids load-order issues
Fix custom external fact loader's weights

Because facter doesn't expose the weight as a customizable value, we
need to override the constant. You can't do that in a subclass:

```ruby
class A
  FOO="A"
  def foo; FOO; end
end

class B < A
  FOO="B"
end

A.new.foo # => "A"
B.new.foo # => "A"

class A
  def foo; self.class::FOO; end
end

A.new.foo # => "A"
B.new.foo # => "B"
```

So, we copy the `#load` method :(
Merge pull request #116 from boxen/apply-external-fact-weights

Apply external fact weights
Remove homebrew refs from top-level env.sh

These should get set by a script controlled in boxen/puppet-homebrew
Merge pull request #117 from boxen/no-homebrew-in-env-sh

Remove homebrew refs from top-level env.sh
Use homebrew_root to determine the homebrew dir
Merge pull request #118 from lstoll/use_homebrew_root

Use homebrew_root to determine the homebrew dir
Simplify personal config as hiera-managed params
Merge pull request #119 from boxen/simplified-personal-configs

Simplify personal config as hiera-managed params
Merge remote-tracking branch 'upstream/master'