updates for jetty 9.1
Merge branch 'jetty91' of github.com:toffaletti/dropwizard into toffaletti-jetty91

Conflicts:
	dropwizard-jetty/pom.xml
	dropwizard-logging/src/main/java/io/dropwizard/logging/AsyncAppender.java
	dropwizard-servlets/pom.xml
	dropwizard-testing/pom.xml
	pom.xml
Upgrade to Jetty 9.2.3.v20140905
Merge branch 'toffaletti-jetty91', closes #453
Upgrade to Guava 18.0