Cleaned up code and did some other minor improvements

* Cleaned up some code
 * Got rid of some variables that might have been kept in memory without them needing to be there.
 * Cleaned up `main.onEnable()` by moving all updater related code to `UpdateChecker` class

* Improved some language strings
 * Improved chat notifications sent to people after requesting their god items (`main`)
 * Fixed a typo somwhere in `main`, though that code might have been moved to `UpdateChecker` already
 * Small languagual improvements in `plugin.yml`

Happy coding!