For created_at of a post, Use UTC time as Facebook created_time

[kangkyu]

in the Facebook response

created_time = "2018-04-13T15:00:01+0000" 

but current way with strptime it parses into a local time, that is not exact

require 'time'
# => true
Time.strptime(created_time,  '%Y-%m-%dT%H:%M:%S+0000')
# => 2018-04-13 15:00:01 -0700
Time.parse created_time
# => 2018-04-13 15:00:01 +0000

[coveralls]

Coverage increased (+0.007%) to 97.989% when pulling 0bd453c on parse-time into 9f1c450 on master.