[README] Add pip git install option

Author: mpsonntag

README.md

@@ -33,6 +33,14 @@ examples can be found at our odML [project page](https://g-node.github.io/python
 pip install odml
 ```
 
+To install the latest development version of odml you can use the git installation option of pip:
+
+```
+pip install git+https://github.com/G-Node/python-odml
+```
+
+Please note that this version might not be stable.
+
 ## Tutorial and examples
 
 - We have assembled a set of