Fix TESTING.md Markdown list syntax; no content changes

[softmoth]

The present indentation isn't valid Markdown, and breaks the display when viewing the rendered file, as on Github. Please compare:

• Old: https://github.com/mustache/spec/blob/f75ffbf0a90e6ccecb11df58cdb4cc400ac2919d/TESTING.md

  • Numbering goes 1, 2, 3 (wrong), 4 (wrong), 2.1 (out-dented, not part of the list), 3, 4.
  • Bulleted list under section 2.1 is entirely preformatted, rather than rendered as the intended list items

• New: https://github.com/softmoth/mustache-spec/blob/format-testing-doc/TESTING.md

This patch moves what was "item" 2.1 back under item 2 without an extra list item. Unfortunately, Markdown doesn't handle this particular structure elegantly as far as I know.

It also switches to backtick quotes for all literals.

[jgonggrijp]

This looks good to me, but I suspect that the top-level items 3 and 4 (in your new version) were also supposed to be subitems of the top-level item 2. What do you think?

[softmoth]

Yes, you're right. Commit amended.