Shutdown async client properly
gracefully handle responses with no entity; provide response code as error_message in cases where no error_message data is returned (eg. 401 Not Authorized when using Elastic with Authentication plugins)
Merge branch 'master' of https://github.com/davidconnard/Jest into davidconnard-master

Conflicts:
	src/main/java/io/searchbox/client/AbstractJestClient.java
Merge branch 'master' of https://github.com/davidconnard/Jest into davidconnard-master

Conflicts:
	src/main/java/io/searchbox/client/AbstractJestClient.java