Move included classes into an includes directory.

[GaryJones]

This somewhat mirrors WP itself, with classes being held in a [wp-]includes directory.

[bradyvercher]

This is how I handle pretty much all my plugins, so I like this change.

[GaryJones]

With usually only a few class files, I've not been too worried, and I didn't have a logical pattern on what should go where. Then:

a) I've been looking more at package.json, Grunt files, .jshintrc and other development / build-related files. Having them potentially in root then makes putting classes into a subfolder.

b) it occurred to me to follow WP itself for the directory name(s). Instead of lib, inc or other variations, stick with includes, which is used in both the WP root (with a wp- prefix) and inside wp-admin.

With those two realisations, my plugins are going to be heading that way too.