fixes gh-591

EurekaBootStrap implements ServletContextListener which causes problems because of early instantiation.

fixes gh-664

* pull625:
  Refactor SimpleHostRoutingFilter

Removed deprecated HttpClient APIs, exposed method to override client, fixed ignoredHeaders

* multiple_monitoring:
  Enables hystrix monitoring of multiple services on a single server.

* create-httpclient-ribbon-command:
  an Apache http client zuul ribbon command

This is an implementation of a RibbonCommand and a factory which makes
use of a loadbalancing http client based on apache's http-components
http-client.
With this command/factory it is possible to route PATCH http requests
via zuul/ribbon as well.

fixes gh-412

* pull655:
  Add support for placeholders in @FeignClient definitions

Includes name and url attributes.

fixes gh-414

fixes gh-657

fixes gh-651

fixes gh-623

Logging each request in the proxy is too verbose and inconsistent
with other Spring MVC logging.

* metrics-aop-fix:
  RestTemplate metrics collection join point now returns a value

Also changes pointcut to use the interface so you don't need
proxyTargetClass=true.

Fixes gh-636

fixes gh-635

* feign-no-content-test:
  Feign handling unparameterized ResponseEntity

fixes gh-612

so that Eureka InstanceInfo (which is designed to be immutable)
can effectively be mutated (by using a different instance) after the
dynamic port is available.

fixes gh-570 ... again

Reword to avoid broken AsciiDoc formatting.

Allows non-eureka based InstanceDiscovery.
Allows custom InstanceDiscovery.

fixes gh-566

fixes gh-589

* metrics-test-fixes:
  Fix flaky Servo tests by avoiding DefaultMonitorRegistry

* metrics:
  Expanded metrics support to include Servo, Spectator, and Atlas

* For Java 8 users, Spectator is the recommended metrics library as Servo is now deprecated in favor of Spectator
* Servo support now needs to be specifically enabled via @EnableServo, even if servo-core is included on the classpath
* Added starter modules for both Spectator and Atlas support
* ServoMetricReader defines a convention for mapping tag-based metrics to hiearchical names for rendering by the Actuator /metrics endpoint