* Initial scaffolding of the host summary endpoint
* inmem datastore implementation of GenerateHostStatusStatistics
* HostSummary docstring
* changing the url of the host summary endpoint
* datastore tests for GenerateHostStatusStatistics
* MySQL datastore implementation of GenerateHostStatusStatistics
* <= and >= to catch exact time edge case
* removing clock interface method
* lowercase error wraps
* removin superfluous whitespace
* use updated_at
* adding a seen_at column to the hosts table
* moving the update of seen_time to the caller
* using db.Get instead of db.Select
