Fanova, Pairs of Variable Plots, AttributeError: 'CategoricalHyperparameter' object has no attribute 'lower'

Hi,
If I want to create the fanova plots, the single variable plots work, but pairs fail:

```
>>> python3.5 /home/schirrmr/programs/ParameterImportance/scripts/evaluate.py --scenario_file scenario.txt --history 'runhistories-shared/runhistory*.json' --modus fanova
INFO:Importance:Reading Scenario file and files specified in the scenario
INFO:smac.scenario.scenario.Scenario:Reading scenario file: deep4_scenario.txt
INFO:smac.scenario.scenario.Scenario:Output to PIMP_fanova_2017_06_06_14:20:34
INFO:Importance:Reading Runhistory
INFO:Importance:Combined number of Runhistory data points: 1038
INFO:Importance:Converting Data and constructing Model
INFO:Importance:Setting up Evaluation Method
INFO:Importance:Running evaluation method fANOVA
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/allow_crash.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/data_folder.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/do_batch_norm.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/double_time_convs.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/drop_prob.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/exponential_demean_factor.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/exponential_standardize_factor.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/filter_length_2.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/filter_length_3.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/filter_length_4.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/filter_time_length.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/final_dense_length.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/first_nonlin.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/first_pool_mode.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/last_seizure_train_ms.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/later_nonlin.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/later_pool_mode.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/n_chans.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/n_epochs.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/non_seiz_to_seiz_factor.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/num_filters_2.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/num_filters_3.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/num_filters_4.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/num_filters_spat.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/num_filters_time.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/only_return_exp.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/pool_time_length.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/pool_time_stride.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/resample_mean_pred_ms.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/run_file.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/sample_by_preds.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/sampling_rate.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/save_folder.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/split_first_layer.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/threshold.png
creating PIMP_fanova_2017_06_06_14:20:34_run1/fanova/['drop_prob', 'filter_length_2'].png
Traceback (most recent call last):
File "/home/schirrmr/programs/ParameterImportance/scripts/evaluate.py", line 52, in
importance.plot_results(name=os.path.join(save_folder, args.modus))
File "/home/schirrmr/programs/ParameterImportance/pimp/importance/importance.py", line 254, in plot_results
self.evaluator.plot_result(name)
File "/home/schirrmr/programs/ParameterImportance/pimp/evaluator/fanova.py", line 68, in plot_result
vis.create_all_plots(name)
File "/home/schirrmr/.local/lib/python3.5/site-packages/fanova/visualizer.py", line 57, in create_all_plots
self.plot_pairwise_marginal(combi, **kwargs)
File "/home/schirrmr/.local/lib/python3.5/site-packages/fanova/visualizer.py", line 114, in plot_pairwise_marginal
lower_bound = self.cs_params[p].lower
AttributeError: 'CategoricalHyperparameter' object has no attribute 'lower'
```

If you need more context: http://nbviewer.jupyter.org/gist/robintibor/6dad6629987cd66b060503bc43e4e2bc/Hyperparameter_June_Report.ipynb

Reproduce the failure with scripts/evaluate.py and the provided scenario and runhistory files, then trace plotting through pimp/importance/importance.py and pimp/evaluator/fanova.py into fanova/visualizer.py. Confirm that single-variable and pairwise fANOVA plots are all generated without the reported CategoricalHyperparameter AttributeError.

Written by the indexing model from the issue text.