Update collation to utf8mb4

Relates to #314 ( https://github.com/usgs/earthquake-event-ws/pull/314 )

Added in mysql 5.5, and can be considered when older versions are no longer supported.

Shouldn't be critical for this application yet, but appears to be the recommended practice. Plus would support emojis in place names :)

• This ticket was migrated from earthquake-event-ws in github ( https://github.com/usgs/earthquake-event-ws/issues/315 )