text: Title: Topic 2 Workbook issue
  Body: In >topic2_part2_telecom_churn_tsne.ipynb
  
  ```
  fig, axes = plt.subplots(nrows=3, ncols=4, figsize=(16, 10))
  
  for idx, feat in  enumerate(features):
      sns.boxplot(x='Churn', y=feat, data=df, ax=axes[idx / 4, idx % 4])
      axes[idx / 4, idx % 4].legend()
      axes[idx / 4, idx % 4].set_xlabel('Churn')
      axes[idx / 4, idx % 4].set_ylabel(feat);
  ```
  would yield following error
  ```
  IndexError                                Traceback (most recent call last)
  <ipython-input-15-b3733e9b0263> in <module>()
        2 
        3 for idx, feat in  enumerate(features):
  ----> 4     sns.boxplot(x='Churn', y=feat, data=df, ax=axes[idx / 4, idx % 4])
        5     axes[idx / 4, idx % 4].legend()
        6     axes[idx / 4, idx % 4].set_xlabel('Churn')
  
  IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices
  ```
  Can be fixed by either replacing `idx / 4` -> `int(idx / 4)` or `idx / 4` -> `idx // 4`
  