DOC: Updates to contribution guide

Updates to the contribution guide in preparation for the hack session.

Principal changes are the addition of ## Unit Testing, and modifications to the description of commit messages to reflect adoption of scipy standard

CONTRIBUTING.md

@@ -199,7 +199,19 @@ $ git clone git@git.ligo.org:albert.einstein/bilby.git
 ```
 
 replacing the SSH url to that of your fork. This will create a directory
-`/bilby` containing a local copy of the code. From this directory, you can run
+`/bilby` containing a local copy of the code.
+
+It is strongly advised to perform development with a dedicated conda environment.
+In depth instructions for creating a conda environment may be found at the relevant
+[conda docs](https://conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html#activating-an-environment),
+but for most purposes the commands
+
+```bash
+$ conda create -n my-environment-name python=3.X
+$ conda activate my-environment-name
+```
+
+will produce the desired results. Once this is completed, one may proceed to the `/bilby` directory and run
 
 ```bash
 $ pip install -e .