Add hexstring tests for frame header encoding

[yschimke]

Before vs After

         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 00 00 00 1a 00 01 00 20 00 00 00 00 00 00 00 00 |....... ........|
|00000010| 00 00 03 e8 00 00 00 00 00 00                   |..........      |
+--------+-------------------------------------------------+----------------+


         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 00 00 00 1a 00 01 20 00 00 00 00 00 00 00 00 00 |...... .........|
|00000010| 00 00 03 e8 00 00 00 00 00 00                   |..........      |
+--------+-------------------------------------------------+----------------+

[yschimke]

Not sure what you think about unit testing the hex dump of the header bytes for frames?

    assertEquals(
        "0000003a000130000000000000000000000003e90000138d",
        ByteBufUtil.hexDump(encodedFrame.getByteBuffer().array(), 0, 24));

[stevegury]

I like the idea of unit-testing the hex dump: easy to spot and fix errors !

[stevegury]

👍
If you don't mind, I propose to batch all breaking changes.
So let's keep the PR open for now.

[stevegury]

@yschimke could you merge master?