README udpated with all valid items

Merge branch 'OleksiiBrylin-fixed-amount'

5.8 Laravel support

Merge pull request zgabievi#42 from yuriymartini/master

[FIX] Update Rewardable.php

Update README.md

isSecondUsageAttempt method explanation

Update composer.json

add support for Laravel 5.7

Merge pull request zgabievi#28 from abhij89/master

update: bug fix config.php

intergrity violation fixes, and code cleanup

Update promocodes.php

add new config params

Merge pull request zgabievi#21 from mpociot/fix-exception-names

Fix exception names