document Requester usage example and more details (#14)
deprecate ResourceRequest.release() method, use cancel() instead (#14)
add Requester.cancel_all() method (#14)

make more changes to the state transition table
make requester example runnable, but not yet automated (#16)
move exceptions to a separate module, define in top-level namespace (#15)
add exceptions module to docs (#15)
make example_requester match the doc version
document exception namespace (#15)
add rostest for example_requester.py (#16)
speed up example_requester test (#16)
include exampler_requester test case literally in the documention (#16)

eliminates redundant code maintenance
convert example requester to a simpler class implementation (#16)
add scheduler example, not automated yet (#17)
minor scheduler example improvements (#17)