Update TGMPA class

[GaryJones]

2.3.6 to 2.5.0

[JohnLauber]

Thanks for the pull request!

[jrfnl]

@JohnLauber You may also want to adjust the config as some settings were deprecated in v2.4.0 and new ones introduced in v2.5.0.

For more information on the current settings: http://tgmpluginactivation.com/configuration/

Most notable changes:

• you may want to add the is_callable setting to the plugins array for WPSEO to catch both the free and the premium version - see https://github.com/TGMPA/TGM-Plugin-Activation/blob/develop/example.php#L91
• 'parent_menu_slug' and 'parent_url_slug' were removed in 2.4.0. Similar functionality was re-introduced in 2.5.0 with the 'parent_slug' and 'capability' config options.
• A number of new strings were introduced. If you have translations available, you may want to consider giving back as TGMPA intends to start providing native translations.

[JohnLauber]

Thanks Juliette. I'll take a look at that.