Fix logging of invalid Unicode data

The io:put_chars/1 function attempts to handle unicode conversions. This
would break when attempting to log a binary like <<255>> (which happens
to exist in #view_query_args{}). This just switches the call to
io:format/2 which does no Unicode conversion.

This bug should only affect dbcore nodes where no rsyslog host is
specified (namely, local development clusters).

BugzId: 30437
Merge pull request #4 from cloudant/30437-fix-bad-unicode-logs

Fix logging of invalid Unicode data