create a new ShardState class for tracking Shard State
use ShardState objects for reads and writes
replace Util.formatStateColumnName
move ShardState-specific code out of Util into ShardState
rename ShardState to SlotState
move string-representation of slotstate to the serializer
Simplify slotFromFinerSlot computation
Fix NPE when updating a coarser slot's stamp; Typo fixes
Add a log statement
Merge pull request #209 from lakshmi-kannan/bf_fix_slot_stamp_npe

Fix NPE when updating a coarser slot's state
Add histogram rollup merge tests; Fix method names
Merge pull request #210 from lakshmi-kannan/bf_histogram_rollup_fixes

Add histogram rollup merge tests; Fix method names
Refactor QueryStringDecoderAndRouter
Merge pull request #211 from chinmay-gupte/chinmay/refactor_QueryStringDecoderAndRouter

Refactor QueryStringDecoderAndRouter.
rename timer.count_ps -> timer.rate.  That's what it is after all.
Merge pull request #213 from gdusbabek/timer_count_ps_rename

Rename TimerRollup.count_ps to TimerRollup.rate.
improve slot state tests. better separation between SlotState and its serialization
add a test case illustrating real-life issues with granularityFromPointsInInterval
improve granularityFromPointsInInterval algorithm
update existing granularity unit tests