update development instructions

Author: francescobrivio

README.md

@@ -115,7 +115,7 @@ print(fpu.get_info())
     ```
 1. Go into the Conifer project directory: `cd conifer`
 1. Install the python development dependencies: `pip install -r dev_requirements.txt`
-1. Run an example: `PYTHONPATH="$(pwd):${PYTHONPATH}" && python examples/sklearn_to_cpp.py`
+1. Run an example: `export PYTHONPATH="$(pwd):${PYTHONPATH}" && python examples/sklearn_to_cpp.py`
 1. Run a single unit test: `pytest tests/test_multiclass.py`
 1. Run all the unit tests: `pytest`
 

dev_requirements.txt

@@ -6,3 +6,4 @@ scikit-learn
 xgboost<2.0.0
 pybind11
 ydf
+pandas