Auto-detect # of conditions in wiigwaas.py

MJ had to make the following changes:
```
-    EXP_ITEMS_FILE_NAME = './experimental_items/experimental_items_small.csv'
-    NUMBER_OF_CONDITIONS = 4
+    EXP_ITEMS_FILE_NAME = './experimental_items/experimental_items_marcella.csv'
+    NUMBER_OF_CONDITIONS = 6
```

This shouldn't be necessary! Make it so that NUMBER_OF_CONDITIONS is auto-detected given the .csv.