Vmeyet/wfu 3839/fix specific share nagios

I've put the had_enough_data in nagios_check.py and added the aggregation possibility
(what was done in the review of work4us/WFU-3520)

I didn't added the reduce function for mongo aggregation, since the aggregation framework goals is to avoid further map-reduce (http://docs.mongodb.org/manual/applications/aggregation/). but I needed to modify a little the return value.

this is paired with https://github.com/Work4Labs/work4us/pull/3102