Add README

README.md

+[NOMAD Laboratory CoE](http://nomad-coe.eu) parser for [BigDFT](http://bigdft.org/)
+
+The original repository lives at
+    https://gitlab.mpcdf.mpg.de/nomad-lab/parser-wien2k
+but you probably want to checkout
+    https://gitlab.mpcdf.mpg.de/nomad-lab/nomad-lab-base
+to also get all dependencies.