Use tilde character (~) instead of dot (.) for URL-safe Base64 coding

The dot character is excluded from auto-linking in most email clients
and is ambiguous in all other contexts when occurring at the end of a
URL. The tilde character, being the only unreserved character for use
in URLs that remains, as per RFC 3986, is thus a good alternative.

src/Base64.php

@@ -11,7 +11,7 @@ namespace Delight\Auth;
 final class Base64 {
 
 	const SPECIAL_CHARS_ORIGINAL = '+/=';
-	const SPECIAL_CHARS_SAFE = '._-';
+	const SPECIAL_CHARS_SAFE = '~_-';
 
 	public static function encode($data, $safeChars = false) {
 		$result = base64_encode($data);