Switched to guava and java std apis for exception throwing

CommonUtil exception methods now "return" the exception so Java's dead-code checker can find dead code.  Updated all the code to "throw" the return.  This patch doesn't change any real logic, its more of relying on java's dead code checker.


Also, the functions can be replaced by functions in guava.  Would it be good to remove this code and replace it with guava's?  If thats ok, I can update the patch to do that.
In this case, how about also excluding the guava dependency from curator?