cleaned up caching and small fixes

tests/test_analysis.py

@@ -27,6 +27,19 @@ def test_image_calculations():
               453842.6]
     assert np.allclose(res["JF16T03V01_intensity"], intensity)
 
+def test_joblib_memory():
+     """ We need joblib for fast caching of intermediate results in all cases. So we check
+         if the basic function caching to disk works.
+     """
+     def calc_example(x):
+          return x**2
+     
+     calc_cached = cristallina.analysis.memory.cache(calc_example)
+
+     assert calc_cached(8) == 64
+     assert calc_cached.check_call_in_cache(8) == True
+
+
 def test_minimal_2d_gaussian():
 
     image = np.array([[0,0,0,0,0],