opStrategy and ordering for ArithmeticPostAgg

Fixes #510
fix some rt cleanup and failure edge cases
address cr
Updates Cassandra example documentation.

Updates the required properties to enable Cassandra as deep storage.
Also adds more information about how to create the required keystore,
and which properties files need to be modified to support Cassandra.
Also adds syntax highlighting to the provided example code.

Additionally, moves Cassandra Deep Storage documentation out into the
actual documentation hierarchy with appropriate linkage. A stub
README.md is left in the example directory to provide a useful landing
page for existing weblinks to the original documentation.
address cr
add more logging
Merge pull request #681 from metamx/fix-rt

fix some rt cleanup and failure edge cases
Merge pull request #680 from lexicalunit/update-cassandra-example

Updates Cassandra example documentation.
prepare for next release
[maven-release-plugin] prepare release druid-0.6.145
[maven-release-plugin] prepare for next development iteration
fix
handle arithmeticEx
better comment
review comment - better way to handle it
Merge pull request #692 from metamx/handle-arithmetic-ex

Handle arithmetic exception for overlow
truncate segmentGranularity
Merge branch 'arithmetic-op-strategies' of https://github.com/metamx/druid into handle-arithmetic-ex
Revert "Merge branch 'arithmetic-op-strategies' of https://github.com/metamx/druid into handle-arithmetic-ex"

This reverts commit 5245422a62a2cccb27fef1d719c62bc2126ba5b7, reversing
changes made to fe03476c53cd3e8948368097394cfb1cd75e4e30.
Merge pull request #693 from metamx/handle-arithmetic-ex

Handle arithmetic ex - additional commit for PR #692