catch e, but return err

[pmelisko]

In fileAnalyze function (lib/require-analyzer.js) there is bug, if there is something wrong in detective.find (i.e. es6/7 features in my case) a get empty result. It is caused by calling callback with null (err instead of e, see that second callback in code below)

fs.readFile(options.target, function(err, data){
    if(err) return callback(err);

    var files;

    try {
      files = detective.find(data.toString('utf8'));
    } catch(e){
      return callback(err);
    }