STORM-87 fail fast on ShellBolt exception
STORM-87 code change accorrding to comments
1. log level change to error
2. use exit instead of halt to terminate jvm
Merge branch 'master' of https://github.com/apache/incubator-storm into STORM-87

Conflicts:
	storm-core/src/jvm/backtype/storm/task/ShellBolt.java
use log-error instead of log-message in exit-process!
Merge branch 'STORM-87' of https://github.com/xiaokang/incubator-storm into STORM-87

STORM-87: fail fast on ShellBolt exception
Added STORM-87 to Changelog