Narrow helper influence

Hi,

I found that we cannot use [Faraday][faraday] gem in Serverspec examples because it raise an error like this:

```ruby
# faraday_spec.rb
require 'serverspec'                                                                                                                           
require 'faraday'

describe Faraday do
  it do
    conn = Faraday.new url: 'http://example.net'
    response = conn.get '/'
    response.body.should include 'Example Domain'
  end
end
```

    $ bundle exec rspec faraday_spec.rb
    F                                                                                                                                          

    Failures:

      1) Faraday
         Failure/Error: conn = Faraday.new url: 'http://example.net'
         NoMethodError: undefined method `path' for "http://example.net":String

           undefined method `path' for "http://example.net":String
         # ./faraday_spec.rb:6:in `block (2 levels) in <top (required)>'

    Finished in 0.03188 seconds
    1 example, 1 failure

    Failed examples:

    rspec ./faraday_spec.rb:5 # Faraday

It is why this occurs that Faraday sees whether `url` argument responds to `host` message or not to judge to parse it by `URI()` or so: https://github.com/lostisland/faraday/blob/v0.9.0.rc7/lib/faraday/utils.rb#L243

I think it is essentially problem that including `Serverspec::Helper::Type` at top level context has too wide influence although it may be reasonable to send a pull request to Faraday project to ask not to use `respond_to?(:host)`.
So, I send the pull request to this project.

Could you consider about that?

Thank you.

[faraday]: https://github.com/lostisland/faraday