Prevent unnecessary query call when model exists (spatie#143)

Do not hardcode table name as it can be changed in config (spatie#142)

* Do not hardcode table name as it can be changed in config

* Only if model is actually extending Eloquent

* We need to define existing and migrated table name

* Late coding means typos.

* Oh, we need PHP 7 support then.

Update TranslationLoaderManager.php (spatie#141)

* Update TranslationLoaderManager.php

Avoid loading translation from the DB when the table does not yet exist.

* Update TranslationLoaderManager.php

wip

drop support for laravel 5.8

Update CHANGELOG.md

Fix styling

Update CHANGELOG.md

Fix changelog

Exclude bad combos