Merge pull request #93 from MiguelSi6/patch-1

Add Imperial Gallons to Volume.php

Author: triplepoint

source/PhysicalQuantity/Volume.php

@@ -148,6 +148,15 @@ protected static function initialize()
         $newUnit->addAlias('gallons');
         $newUnit->addAlias('us gal');
         static::addUnit($newUnit);
+
+        // Imperial Gallon
+        $newUnit = UnitOfMeasure::linearUnitFactory('imp gal', 4.54609e-3);
+        $newUnit->addAlias('imperial gallon');
+        $newUnit->addAlias('imperial gal');
+        $newUnit->addAlias('imp gallon');
+        $newUnit->addAlias('impg');
+        static::addUnit($newUnit);
+        
         // Quart
         $newUnit = UnitOfMeasure::linearUnitFactory('qt', 9.4635295e-4);
         $newUnit->addAlias('quart');