Allow users to select the comments provider

[hszhakka]

The users can select their comments provider by configuring:

minima:
  comments_provider: # Configure the comments provider here (default: disqus)

For example, if the comments provider is discourse, the user needs to create a file _includes/discourse_comments.html and put all script code of discourse into that file.

[DirtyF]

What comment providers can we list here? Do they all implement the same as Disqus?

[MichaelCurrin]

If you get the value and it is not set on the page, it will be null and then null != false will be truthy.

---
---
{{ page.fizz | jsonify }}

Result is null

So while page.comments != false is unreliable, then page.comments == true will only be truthy if the value is true and not if it is false or missing.

Suggested change

	{% if page.comments != false and jekyll.environment == "production" %}
	{% if page.comments == true and jekyll.environment == "production" %}

OR

  {% if page.comments and page.comments == true and jekyll.environment == "production" %}