Closing #656 and updating documentation

Signed-off-by: Preetham <me@preetham.in>
diff --git a/system/helpers/captcha_helper.php b/system/helpers/captcha_helper.php
index 8c2cfa4..4398d31 100644
--- a/system/helpers/captcha_helper.php
+++ b/system/helpers/captcha_helper.php
@@ -71,7 +71,7 @@
 			'font_path'	=> '',
 			'expiration'	=> 7200,
 			'word_length'	=> 8,
-			'font_size' =>16,
+			'font_size'		=>16,
 			'pool'		=> '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ',
 			'colors'	=> array(
 				'background'	=> array(255,255,255),
@@ -194,13 +194,13 @@
 		$use_font = ($font_path !== '' && file_exists($font_path) && function_exists('imagettftext'));
 		if ($use_font === FALSE)
 		{
-			$font_size = $font_size>5?5:$font_size;
+			($font_size >= 5) && $font_size = 5;;
 			$x = mt_rand(0, $img_width / ($length / 3));
 			$y = 0;
 		}
 		else
 		{
-			$font_size = $font_size>30?30:$font_size;
+			($font_size > 30) && $font_size = 30;
 			$x = mt_rand(0, $img_width / ($length / 1.5));
 			$y = $font_size + 2;
 		}