loading the admin class only if the dashboard is being loaded

fixes #104
moving all of the admin-specific functionality into the admin subdirectory

related #100
removing files from the main plugin directory in favor of admin and public specific directories

related #100
adding public and admin comments. conditionally loading the admin class.

related #104
moving all public related code to a self-contained subdirectory

related #100
updating a comment
removing files from the plugin root

related #100
updating the change log, moving the previous untagged 2.6.0 notes into the official, forthcoming 2.6.0 tag.
updating typos in the read. props @grappler.
adding empty includes directories as a place for shared functionality

related #100
updating the readme
finalizing the change log
Place the TODOs in the correct position
Merge pull request #110 from grappler/patch-1

Place the TODOs in the correct position
Fix $plugin_basename to allow plugin_action_links

With the move to /admin and /public directory, the class-plugin-name-admin.php needed to be changed to use __DIR__ instead of __FILE__ to create the $plugin_basename, otherwise the hook would be something like plugin_action_links_plugin-name/admin/plugin-name.php which doesn't work.
Merge pull request #116 from neverything/patch-1

Fix $plugin_basename to allow plugin_action_links
Fix textdomain not loading

Before: public/languages
After: plugin-name/languages
Merge pull request #120 from neverything/patch-2

Fix textdomain not loading