Show sleep tracking date as "night of" rather than "day of"

From Anonymous on 2016/08/28 01:26:50 +0000

If I sleep on Friday night, the sleep tracking log entry says Saturday. But I want it to say instead; Friday night’s sleep, rather than the morning of Saturday’s sleep.

Copied from original feature request: http://urbandroid.uservoice.com/forums/264867-sleep-as-android/suggestions/15842482-show-sleep-tracking-date-as-night-of-rather-than