Add pytest command examples to the README

Author: 1fish2

README.md

@@ -104,8 +104,20 @@ There are more command line features in test_arrow:
 
     > python -m arrow.test.test_arrow --time
 
+More examples:
+
+    > python -m arrow.test.test_hang
+
+    > pytest -m arrow/test/test_arrow.py
+
+    > pytest -k flagella
+
 ## Changelog
 
+### Version 0.4.4
+
+* Can pickle StochasticSystem instances.
+
 ### Version 0.3.0
 
 * Introduced backwards-incompatible API change for supplying rates at `evolve()` time rather than `__init__()` for `StochasticSystem`.