Expand on editing index.md in Episode 2

Given we have recommended Nano as core editor, it would be good to practise using it to edit index.md. I suspect most Instructors would do this anyway.

Breaking this step down into several paragraphs should make it less overwhelming.

To make the step portable to Nano, I think we should include an instruction to close the file. It will also help declutter when using other editors, since we don't edit the file again for a while.

Closes #124.

Author: alex-ball

episodes/02-getting-started.md

@@ -95,7 +95,7 @@ Vi and Vim are popular editors for users of the BASH shell. If you will be using
 ::::::::::::::::::::::::::::::::::::::::::::::::::
 
 Any text editor can be made default by adding the correct file path and command line options (see [GitHub help](https://help.github.com/articles/associating-text-editors-with-git/)).
-However, the simplest `core.editor` value is  `"nano -w"` on Mac, Windows, and Linux.
+However, the simplest `core.editor` value is  `"nano -w"` on Mac, Windows, and Linux, which will run the Nano text editor directly in your shell.
 
 For example:
 
@@ -242,9 +242,17 @@ Changes to be committed:
 If we are using colourised output, we will see that the filename has changed colour (from red to green). Git also tells us that there
 is a new file to be committed but, before we do that, let's add some text to the file.
 
-We will open the file `index.md` with any text editor we have at hand (e.g. Notepad on Windows or TextEdit on Mac OSX) and enter `# Hello, world!`. The
-hash character is one way of writing a header with Markdown. Now, let's save the file within the text editor and check if Git
-has spotted the changes.
+We will open the file `index.md` with a text editor. If you set Nano as your `core.editor` value, this would be a good time to try it out:
+
+```bash
+nano -w index.md
+```
+
+If you don't want to try Nano, use whatever text editor you feel comfortable with (e.g. Notepad on Windows or TextEdit on macOS) to open the file.
+
+When you have the file open, enter `# Hello, world!`. The hash character is one way of writing a header with Markdown. Then save the file and close the text editor.
+
+Now, let's check if Git has spotted the changes:
 
 ```bash 
 $ git status
@@ -289,11 +297,11 @@ $ git commit -m 'Add index.md'
  create mode 100644 index.md
 ```
 
-We can see that one file has changed and that we made one insertion, which was a line with the text '#Hello, world!'.
+We can see that one file has changed and that we made one insertion, which was a line with the text '# Hello, world!'.
 We can
 also see the commit message 'Add index.md', which we added by using the `-m` flag after `git commit`.
 The commit message is used to record a short, descriptive, and specific summary of what we did to help us remember later on without having to look at the actual changes.
-If we just run `git commit` without the `-m` option, Git will launch nano (or whatever other editor we configured as `core.editor`)
+If we just run `git commit` without the `-m` option, Git will launch Nano (or whatever other editor we configured as `core.editor`)
 so that we can write a longer message.
 
 Having made a commit, we now have a permanent record of what was changed,