Versioneer

This MR enables Versioneer to have a consistent way for pystencils to get a version string

pystencils_tests/test_version_string.py

@@ -2,4 +2,10 @@ import pystencils as ps
 
 def test_version_string():
     version = ps.__version__
-    assert version.split('.')[0] == '3'
+    print(version)
\ No newline at end of file
+
+    numeric_version = [int(x, 10) for x in version.split('.')[0:2]]
+    numeric_version.reverse()
+    test_version = sum(x * (100 ** i) for i, x in enumerate(numeric_version))
+
+    assert test_version >= 3
\ No newline at end of file