Strip out non-ascii characters in the folder directory.

The big offender being "::" being in the resource description as it
treats the folder like a URI. "Namespace::Model" => "namespace::model/".

Closes zipmark#93

features/folder_structure.feature

@@ -0,0 +1,34 @@
+Feature: Folder Structure
+  Background:
+    Given a file named "app.rb" with:
+      """
+      class App
+        def self.call(env)
+          [200, {}, ["hello"]]
+        end
+      end
+      """
+    And   a file named "app_spec.rb" with:
+      """
+      require "rspec_api_documentation"
+      require "rspec_api_documentation/dsl"
+
+      RspecApiDocumentation.configure do |config|
+        config.app = App
+      end
+
+      resource "Namespace::Greetings" do
+        get "/greetings" do
+          example_request "Greeting your favorite gem" do
+            expect(status).to eq(200)
+          end
+        end
+      end
+      """
+    When  I run `rspec app_spec.rb --require ./app.rb --format RspecApiDocumentation::ApiFormatter`
+
+  Scenario: Folder structure does not contain ::
+    When  I open the index
+    And   I navigate to "Greeting your favorite gem"
+
+    Then  I should see the route is "GET /greetings"

lib/rspec_api_documentation/views/markup_example.rb

@@ -18,7 +18,7 @@ def respond_to?(method, include_private = false)
       end
 
       def dirname
-        resource_name.downcase.gsub(/\s+/, '_')
+        resource_name.downcase.gsub(/[^0-9a-z.\-]+/, '_')
       end
 
       def filename