title: Hyperopt on text train data: ValueError: zero-dimensional arrays cannot be concatenated
body: <p>I'm using the hyperopt package (version 0.1.2) and I figure out the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:Users\PycharmProjects\script\my_script.py", line 34, in &lt;module&gt;
      estim.fit(xTrain, yTrain)
    File "C:\Users\PycharmProjects\venv\lib\site- 
  packages\hpsklearn\estimator.py", line 746, in fit
      fit_iter.send(increment)
    File "C:Users\PycharmProjects\script\my_script\venv\lib\site- 
     packages\hpsklearn\estimator.py", line 657, in fit_iter
      return_argmin=False, # -- in case no success so far
    File "C:Users\PycharmProjects\script\my_script\venv\lib\site- 
     packages\hyperopt\fmin.py", line 388, in fmin
      show_progressbar=show_progressbar,
    File "C:Users\PycharmProjects\script\my_script\venv\lib\site- 
  packages\hyperopt\base.py", line 639, in fmin
       show_progressbar=show_progressbar)
     File "C:Users\PycharmProjects\script\my_script\venv\lib\site- 
  packages\hyperopt\fmin.py", line 407, in fmin
      rval.exhaust()
    File "C:Users\PycharmProjects\script\my_script\venv\lib\site-packages\hyperopt\fmin.py", line 262, in exhaust
      self.run(self.max_evals - n_done, block_until_done=self.asynchronous)
    File "C:Users\PycharmProjects\script\my_script\venv\lib\site-packages\hyperopt\fmin.py", line 227, in run
  
  self.serial_evaluate()
     File "C:Users\PycharmProjects\script\my_script\venv\lib\site-packages\hyperopt\fmin.py", line 141, in serial_evaluate
       result = self.domain.evaluate(spec, ctrl)
     File "C:Users\PycharmProjects\script\my_script\venv\lib\site-packages\hyperopt\base.py", line 844, in evaluate
       rval = self.fn(pyll_rval)
     File "C:Users\PycharmProjects\script\my_script\venv\lib\site-packages\hpsklearn\estimator.py", line 620, in fn_with_timeout
  raise fn_rval[1]
   ValueError: zero-dimensional arrays cannot be concatenated
  </code></pre>
  
  <p>The original X and y data as a list, and here the following code:</p>
  
  <pre><code>from sklearn.model_selection import train_test_split
  from hpsklearn import HyperoptEstimator, tfidf, svc_poly
  from hyperopt import tpe
  
  
  if __name__ == '__main__':
  
      X_data = ['this is an example text 1', 'this is an example text 2', 'this is an example text 3', 'this is an example text 4'] * 25
      y_data = ['this is just and example label 1', 'this is just and example label 2'] * 50
      print(len(X_data), len(y_data))
  
  
      print(len(X_data), len(y_data))
      xTrain, xTest, yTrain, yTest = train_test_split(
          X_data, y_data,
          test_size=0.22,
          random_state=33)
  
      estim = HyperoptEstimator(
          classifier=[svc_poly('my_poly', degree=3)],
          preprocessing=[tfidf('tfidf')],
          algo=tpe.suggest,
          trial_timeout=180
      )
  
      estim.fit(xTrain, yTrain) # error pops up here
  </code></pre>
  
  <p>I already tried to create a numpy arrays instead list, but the result is always this error. </p>