Add readme.md

README.md

+[NOMAD CoE](http://nomad-coe.eu) parser for "elastic" a program to calculate
+elastic constants.
+
+The original version is available at
+    https://gitlab.rzg.mpg.de/nomad-lab/parser-elastic
+to use it you probably want to recursively clone
+    https://gitlab.rzg.mpg.de/nomad-lab/nomad-lab-base
+to get it plus all its dependencies.