code: function tally(pathname, offenses) {
      var count = offenses.length,
          plural = count > 1 ? 'errors' : 'error';
  
      function perOffense(o) {
          if (!errors[pathname]) {
              errors[pathname] = [];
          }
  
          if (o) {
              errors[pathname].push({
                  line: o.line,
                  col: o.character,
                  msg: o.reason,
                  evidence: o.evidence || ''
              });
          }
      }
  
      log.error([count, plural, 'in', pathname].join(' '));
      offenses.forEach(perOffense);
  }
docs: save array of lint error(s) in object keyed by filename