Version 1.3.5:
	+ Validation of the purchase key is now domain-specific 
	+ Checking for the possibility of updating the theme / plugin with the minimum allowed version is added

Version 1.3.4:
	* Compatibility with WordPress 5.3 is improved

Version 1.3.3:
	* Caching the server's response when theme version checking is improved

Version 1.3.2:
	* Auto activation plugins after update is added

Version 1.3.1:
	* Branch 'release' is added

Version 1.3.0:
	+ List of backups is added to the end of the page "Dashboard - Updates".
	  User can check some backups in the list and restore its (revert theme or plugin to its previous version)
	  or delete checked backups (to save disk space on the server)

Version 1.2.0:
	* Checking version of the current (active) theme is changed.
	+ The ability to back up plugins (themes) before update and restore previously saved versions is added.

Version 1.1.3:
	* Checking version of installed plugins is changed.

Version 1.1.2:
	* Order of checking plugins is changed: instead check all installed plugins,
	  only theme-required plugins (from TGMPA) are checked for updates.
	+ On first installation theme-required plugins also available from the upgrade-servers
	  instead pre-packaged archives.

Version 1.1.1:
	* Check if ThemeREX Updater is not in the TGMPA plugins list before insert it in the list.

Version 1.1.0:
	+ Separate classes for plugins and theme updates are added.
	+ The plugin's options page in admin menu Appearance - ThemeREX Updater is now available.
	+ Update manager run only if current theme is activated or the theme's purchase code is
	  specified in the plugin's options page.

Version 1.0.0:
	+ First release. Main features: allow update theme-specific plugins from upgrade server
	  if theme purchase key is specified.