Update validation.php

Language validation addition for https://github.com/laravel/framework/pull/4599
Merge pull request #2948 from TheShiftExchange/patch-1

Update validation language to include boolean
Update validation.php
Merge commit 'a914718a57dad482cf48d1903f4d96c3f919524e' into cleanup

Conflicts:
	app/lang/en/validation.php