Merge pull request #32 from jwtk/base64padding

#31: fixed base64 url padding bug

src/main/java/io/jsonwebtoken/impl/Base64UrlCodec.java

@@ -82,7 +82,14 @@ protected char[] ensurePadding(char[] chars) {
 
         char[] result = chars; //assume argument in case no padding is necessary
 
-        int paddingCount = chars.length % 4;
+        int paddingCount = 0;
+
+        //fix for https://github.com/jwtk/jjwt/issues/31
+        int remainder = chars.length % 4;
+        if (remainder == 2 || remainder == 3) {
+            paddingCount = 4 - remainder;
+        }
+
         if (paddingCount > 0) {
             result = new char[chars.length + paddingCount];
             System.arraycopy(chars, 0, result, 0, chars.length);