set version number for the first pre-realease

Author: MalteKurz

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: DoubleML
 Type: Package
 Title: Double Machine Learning
-Version: 0.1.0.9000
+Version: 0.0.1
 Authors@R: c(
     person("Philipp", "Bach", email = "philipp.bach@uni-hamburg.de", role="aut"),
     person("Victor", "Chernozhukov", role="aut"),