Added Servo wiring for Zuul global metrics

Conflicts:
	zuul-core/src/main/java/com/netflix/zuul/StartServer.java
	zuul-core/src/main/java/com/netflix/zuul/filterstore/ClassPathFilterStore.java
	zuul-core/src/main/java/com/netflix/zuul/filterstore/FileSystemPollingFilterStore.java
	zuul-core/src/main/java/com/netflix/zuul/filterstore/FilterStore.java
	zuul-core/src/main/java/com/netflix/zuul/filterstore/InMemoryFilterStore.java
Merge pull request #48 from mattrjacobs/global-servo-metrics

Added Servo wiring for Zuul global metrics