Support for 5.6, 5.7, & 5.8! + Tests!

Updates thanks for @namelivia for adding support for Laravel 5.6, 5.7 & 5.8 as well as adding tests for everything!

Laravel 5.x Update

• Better error handling
• Replaced depreacted share function with singleton method
• Updated README.md
• Swapped config method for env

Laravel 4.2 Compatible

4.0

Reverted for Laravel 4.2 compatability

Laravel 5 Compatible

5.0

Update README.md