Updated documentation and documentation tests

Author: okdana

README.md

@@ -41,7 +41,8 @@ By default all values are rounded to the nearest integer.
 ```
 > 513 KiB
 
-Increasing the precision with `setPrecision($precision)` allows the specified amount of digits after the decimal point.
+The default precision can be increased with `setPrecision($precision)`. Increasing the precision allows the specified amount of digits after the decimal point.
+
 ```php
 (new ByteFormatter)->setPrecision(2)->format(0x80233);
 ```
@@ -55,6 +56,13 @@ needed.
 ```
 > 512.5 KiB
 
+The default precision can be overridden on a per-format basis using the optional precision argument to `format()`.
+
+```php
+(new ByteFormatter)->setPrecision(2)->format(0x80233, 4);
+```
+> 512.5498 KiB
+
 Output format
 -------------
 

test/Integration/DocumentationTest.php

@@ -22,6 +22,8 @@ public function testPrecision()
         $this->assertSame('512.55 KiB', (new ByteFormatter)->setPrecision(2)->format(0x80233));
 
         $this->assertSame('512.5 KiB', (new ByteFormatter)->setPrecision(2)->format(0x80200));
+
+        $this->assertSame('512.5498 KiB', (new ByteFormatter)->setPrecision(2)->format(0x80233, 4));
     }
 
     public function testOutputFormat()