rename AMT.CreateHITParameters to AMT.HITParameters
renamed workerPool.py to workerpool.py
add TimeUnit
move AMT.py into crowdsim/agent/
Fix some typos
Let AMT.getHIT() return result only if r.valid
Change the global `DEBUG` to member variable `debug`
fix small mistakes, change the __init__ function of BaseStrategyAssigner
add workerpool_amt.py
fix some errors of BaseStrategyAssigner.__init__()

add parameter `verbose` for the __init__()
change workerpool_amt log format
delete `assignerDeducer` and add `passer`

passer is more general then assignerDeducer and it can pass results
from worker directly.
fix a bug in workerpool_amt
getAssignmentForHIT()[1] is a list now
deducer.passer -> deducer.Passer
some change to AMT.createHIT()

1. accept parameter `responseGroup`
2. return tuple of (HITId, HITTypeId, HITXmlElement) now.
some changes to workerpool_amt

1. allow specify response group in __init__()
2. store hit xml element into hitInfo['HITElement']
3. the parameter list of answerConstructor should be (hitInfo,
   assignment) now
AMT.getAssignmentsForHIT() now accept responseGroup
fix bugs for deducer.Passer
handle the "divide by 0" problems in the evaluation functions