Add feign-eager-instantiation

This tests for NPEs when feign clients are eagerly instantiated, via devtools for example.

feign-eager-instantiation/src/main/java/demo/ExampleClient.java

@@ -0,0 +1,12 @@
+package demo;
+
+import org.springframework.cloud.netflix.feign.FeignClient;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+
+@FeignClient(name = "example", url = "http://example.com")
+public interface ExampleClient {
+
+    @RequestMapping(value = "/", method = RequestMethod.GET)
+    String get();
+}