ChoreStartTime returning incorrect start_time (datetime) and start_time_string

[gtonkin]

StartTime values from the REST API called would looks something like "2016-02-13T05:00+02:00" or "2016-02-13T05:00Z" or "2016-02-13T05:00-02:00"

When retrieving the start_time or start_time_string it appears that the seconds component is added but where timezone is not Zulu, the offset becomes the seconds so you end up with a value like "2016-02-13T05:00:02+02:00". Seconds should always be 00 as you cannot schedule a chore by seconds, only by hours and minutes.