create SpringClientFactory for ribbon to not fail on client creation if LoadBalancer is already created.  SpringClientFactory is not a static factory, but an instance factory.

Remove unused hystrix configuration classes.

This makes perfect sense since there is already support in the API.
Unfortunately Eureka also uses that information to set the Server
zones by default (duh?!) - see DiscoveryClient.getZone(InstanceInfo),
so unless you aggressively update them, the zones will all be the same
in all servers.

I fixed that problem by unconditionally applying the "domain as zone"
guess algorithm, which is fine unless you actually want to use
the Amazon metadata. So that's an outstanding problem

See gh-30

A EurekaInstanceConfig can declare a "zone" in its metadataMap, and then
it will be matched by the RibbonLoadBalancerClient. The zone of a server
is derived from the hostname - it is the whole host name or the host name
excluding the least significant subdomain (period separated identifier).

Fixes gh-29

Additionally added some license headers and @author tags.

fixes #17

added beginnings of a generic DiscoveryClient interface;

Eureka server is itself a eureka client when discovering eureka peers (it gets DiscoverClient from DiscoveryManager).  Make sure DiscoveryManager is initialzed regardless of if the client or server config is invoked first.

fixes gh-18

Add support for Ribbon loadbalancing in RestTemplate via an HttpRequestInterceptor that when supplied a uri such as http://myservice/my/endpoint (where myservice is a service as defined in a service registry, such as Eureka), it replaces 'myservice' with the actual host and port as returned from the configured ribbon loadbalancer.

closes gh-12

Without extracting to autoconfig the @ConditionalOnMissingBean won't
always work because it is dependent on the order of the configuration
classes being processed (and autoconfig always somes last).