Rename `_make` to `pushStack`

[fb55]

The internal method _make is equivalent to jQuery's pushStack. Let's rename it, to make it an official API.

Uncovered in #1656.

[5saviahv]

It would be nice, it is internal in jQuery also, but this way you have at least more information sources available.

[5saviahv]

Interesting why _make wont call directly

new Cheerio(...)

[5saviahv]

in jQuery methods can call for constructor either jQuery(...) or jQuery.pushStack(...). When first one simply creates new jQuery instance. Second one creates new instance and pushes current object into prevObject.

in Cheerio calling _make is basically only way to get access to constructor. I think this way prevObject isnt always previous object.

[fb55]

I decided against doing this, as the semantics don't quite line up.