Allows to use multiple stub converters

with this change all available stub converters on the classpath will be executed to convert the contract. That way you can make such a flow pass:

- from DSL input
- generate Java tests
- produce WireMock stubs
- produce Pact files

fixes #194

docs/src/main/asciidoc/verifier/contract.adoc

@@ -855,6 +855,9 @@ include::{converters_path}/src/main/resources/META-INF/spring.factories[indent=0
 
 The default implementation is the WireMock stub generation.
 
+TIP: You can provide multiple stub generator implementations. That way for example from a single
+DSL as input you can e.g. produce WireMock stubs and Pact files too!
+
 ==== Custom Stub Runner
 
 If you decide to have a custom stub generation you also need a custom way of running