Include linear operator in installation instructions
Since latest features may rely on latest features in linear operator.
@@ -34,6 +34,7 @@ conda install gpytorch -c gpytorch
To upgrade to the latest (unstable) version, run
```bash
+pip install --upgrade git+https://github.com/cornellius-gp/linear_operator.git
pip install --upgrade git+https://github.com/cornellius-gp/gpytorch.git
```
