Fix test version string

pystencils_tests/test_version_string.py

-import pystencils as ps
+import lbmpy
+
 
 def test_version_string():
-    version = ps.__version__
+    version = lbmpy.__version__
     print(version)
 
-    numeric_version = [int(x, 10) for x in version.split('.')[0:2]]
+    numeric_version = [int(x, 10) for x in version.split('.')[0:1]]
     test_version = sum(x * (100 ** i) for i, x in enumerate(numeric_version))
 
-    assert test_version >= 200
\ No newline at end of file
+    assert test_version >= 1