Update README.md

README.md

@@ -11,7 +11,7 @@ Open source multi-objective energy system framework
 
 `osier` is available through [PyPI](https://pypi.org/project/osier/). It may be installed with 
 ```bash
-pip install osier
+python -m pip install osier pyomo==6.4.1
 ``` 
 or by cloning this repository and building from source:
 
@@ -60,4 +60,4 @@ Contributions to `osier` are welcome. For details on how to make bug reports, pu
 
 
 ## Credits
-Some of the documentation infrastructure was inspired by and borrowed from the [`watts` documentation](https://watts.readthedocs.io/en/latest/index.html).
+Some of the documentation infrastructure was inspired by and borrowed from the [`watts` documentation](https://watts.readthedocs.io/en/latest/index.html).