Update CONTRIBUTING.rst

CONTRIBUTING.rst

@@ -175,13 +175,13 @@ To install (and activate) a `conda environment`_ named ``notebook_docs``
 containing all the necessary packages (except pandoc), use::
 
     conda env create -f docs/environment.yml
-    source activate notebook_docs  # Linux and OS X
+    conda activate notebook_docs  # Linux and OS X
     activate notebook_docs         # Windows
 
 .. _conda environment:
     https://conda.io/docs/user-guide/tasks/manage-environments.html#creating-an-environment-from-an-environment-yml-file
 
-If you want to install the necessary packages with ``pip`` instead::
+If you want to install the necessary packages with ``pip``, use the following instead::
 
     pip install -r docs/doc-requirements.txt