Add @FeignClient(primary)

Adds the ability to turn off Spring Cloud Netflix making the feign instances as primary.

fixes gh-1016

docs/src/main/asciidoc/spring-cloud-netflix.adoc

@@ -1127,6 +1127,18 @@ static class HystrixClientFallbackFactory implements FallbackFactory<HystrixClie
 
 WARNING: There is a limitation with the implementation of fallbacks in Feign and how Hystrix fallbacks work. Fallbacks are currently not supported for methods that return `com.netflix.hystrix.HystrixCommand` and `rx.Observable`.
 
+=== Feign and `@Primary`
+
+When using Feign with Hystrix fallbacks, there are multiple beans in the `ApplicationContext` of the same type. This will cause `@Autowired` to work because there isn't exactly one bean, or one marked as primary. To work around this, Spring Cloud Netflix marks all Feign instances as `@Primary`, so Spring Framework will know which bean to inject. In some cases, this may not be desirable. To turn off this behavior set the `primary` attribute of `@FeignClient` to false.
+
+[source,java,indent=0]
+----
+@FeignClient(name = "hello", primary = false)
+public interface HelloClient {
+	// methods here
+}
+----
+
 [[spring-cloud-feign-inheritance]]
 === Feign Inheritance Support