Update readme and fix example
### Python Bindings
```
-python3.7 -m venv .env
+# This expect the rust chain to be nightly
+rustup update
+rustup default nightly
+
+# In this folder:
+python3 -m venv .env
source .env/bin/activate
pip install maturin
-maturin build
+maturin develop --release
+
+# Then test:
+pip install transformers
+python example.py --file <FILE_PATH>
+# or
python example.py
```
