Merge pull request #114 from darxriggs/master

fix cut-n-paste mistake in error message (part2)
use reservoir sampling in pickSegmentToMove to avoid IndexOutOfBoundsException when a segment gets dropped mid-run
add argument checks to dim filters
Merge pull request #115 from metamx/argument-checks

add argument checks to dim filters
remove unused imports
1) Expand logging of unregistering real-time segments to help diagnose strange zookeeper behavior
cleanup - removed extra empty lines

- there should not be any adjacent empty lines
refactoring - made json type infos consistent for all query types