Commit 5fb2fe5

* Change: Remove unnecessary numbering of sole placeholder in string

* Change: Update links to coffee2code.com to be HTTPS

* Change: Update legend image

* Unit tests:

* New: Add tests for `add_css()`, `admin_init()`, `explain_nonce()`, `show_admin_notices()`, `show_legend_image()`

* New: Add test for setting name