added readme

greenGridr/README.md

+# GreenGridr
+
+Package of functions to process [NZ GreenGrid](https://www.otago.ac.nz/centre-sustainability/research/energy/otago050285.html) data.
+ 
+### Terms of code re-use
+
+Read the [License](LICENSE) file.
+
+[YMMV](http://en.wiktionary.org/wiki/YMMV)