Allow 'android-app' url scheme

Referer urls like
"android-app://com.google.android.googlequicksearchbox" are valid and
shouldn't cause an error.

ruby/lib/referer-parser/parser.rb

@@ -86,8 +86,8 @@ def optimize_index!
     def parse(obj)
       url = obj.is_a?(URI) ? obj : URI.parse(obj.to_s)
 
-      if !['http', 'https'].include?(url.scheme)
-        raise InvalidUriError.new("Only HTTP and HTTPS schemes are supported -- #{url.scheme}") 
+      if !['android-app', 'http', 'https'].include?(url.scheme)
+        raise InvalidUriError.new("Only Android-App, HTTP, and HTTPS schemes are supported -- #{url.scheme}")
       end
 
       data = { :known => false, :uri => url.to_s }