Added attribute First Contentful Paint Time

Added attribute first_contentful_paint_time (#2)

* Add $firstContentfulPaintTime

* Add $firstContentfulPaintTime

* Added ability to send x-metrix-* parameters

Version 2.0.0

Replace references of Entrecore and Opsbears for LightningStudio and as such this will break older versions because of the namespace change.

Version 1.0.5

Fix issues with the PHPUnit Tests in Travis CI by updating to latest version of PHPUnit and Phing, update files with changes and therefore can now run on PHP 8.0.

Version 1.0.4

Trying to force update to packagist

Version 1.0.3

Fix issue with the PSR-4 autoloader

Updated with new changes for GTMetrix API

v1.0.2

Update README.md