clarify habitat configuration templates docs
I don't know if this is the right way to convey this information, but it reads clearer to me than what's currently in the docs.
@@ -31,7 +31,11 @@ Chef Habitat can read values that it will use to render the templatized config f
1. `default.toml` - Each plan includes a `default.toml` file that specifies the default values to use in the absence of any user provided inputs. These files are written in [TOML](https://github.com/toml-lang/toml), a simple config format.
1. At runtime - Users can alter config at runtime using `hab config apply`. The input for this command also uses the TOML format.
-1. Environment variable - At start up, tunable config values can be passed to Chef Habitat using environment variables; this most over-riding way of setting these but require you to restart the supervisor to change them.
+1. Environment variable - At start up, tunable config values can be passed to Chef Habitat using environment variables.
+
+When building packages you should prefer supplying values in `default.toml`, then at runtime, and last in Environment variables. Environment variables override default.toml, and runtime config setting using `hab config apply` overrides both default settings and settings provided in environment variables.
+
+Changing settings using environment variables requires you to restart the supervisor in order to pick up the new or changed environment variable.
Here's what we'd add to our project's `default.toml` file to provide a default value for the `recv_buffer` tunable:
