TODO: Move into separate file?
+0.3.0: Considerable speedup by avoiding unneeded copy. Dataclasses used.
+ Mostly API compatible, but repr looks different.
+
+0.2.0: API incompatible changes. Targeted to Python 3 now.
+
0.1.3: Changed stdev computation to avoid negative variance due to rounding errors.
0.1.2: First version published in PyPI.