Added $charList and $type to trim function

Adding the option to trim the string with others characters, not only with the default characters provided by php. Also added the option to define the function which will be used to trim the string, if it's normal trim, left trim or right trim

src/Stringy.php

@@ -4,6 +4,13 @@ namespace Stringy;
 
 class Stringy implements \Countable, \IteratorAggregate, \ArrayAccess
 {
+
+    const TRIM_BOTH = 'trim';
+
+    const TRIM_LEFT = 'ltrim';
+
+    const TRIM_RIGHT = 'rtrim';
+
     /**
      * An instance's string.
      *
@@ -1026,11 +1033,30 @@ class Stringy implements \Countable, \IteratorAggregate, \ArrayAccess
     /**
      * Returns the trimmed string. An alias for PHP's trim() function.
      *
+     * @param string $charList list with characters to be removed
+     * @param int $type which function will be used to trim the string, trim, ltrim or rtrim
      * @return Stringy Object with a trimmed $str
+     * @throws \InvalidArgumentException
      */
-    public function trim()
+    public function trim($charList = " \t\n\r\0\x0B", $type = self::TRIM_BOTH)
     {
-        return static::create(trim($this->str), $this->encoding);
+        if (!is_string($charList)) {
+            throw new \InvalidArgumentException(
+                'Charset list must be a string'
+            );
+        }
+
+        if (!in_array($type, array(
+            self::TRIM_BOTH,
+            self::TRIM_LEFT,
+            self::TRIM_RIGHT,
+        ))) {
+            throw new \InvalidArgumentException(
+                'Type of trim function must be trim (default), rtrim or ltrim, just as native php.'
+            );
+        }
+
+        return static::create($type($this->str, $charList), $this->encoding);
     }
 
     /**