Fixes #45: Autogeneration of Huffman Tables not working

https://github.com/alobbs/libhpack/issues/45

The autogeneration of the Huffman Tables is not working anymore, as Travis is reporting:
> Auto generating Huffman tables
> Checking source
> Parsing source file
> No data could be parsed from input file.

The reason for this is that they removed one redundant column of the table (first *len in bits*).
In previous drafts the format was:
```
              aligned                                  aligned
               to                            len        to     len
               MSB                            in        LSB     in
        sym    as bits                       bits      as hex  bits
       (  0) |11111111|11111111|11110111|010 [27]      7ffffba [27]
       (  1) |11111111|11111111|11110111|011 [27]      7ffffbb [27]
```
Now the format is:
```
                                            code
                    code as bits           as hex   len
     sym           aligned to MSB          aligned   in
                                           to LSB   bits
    (  0)  |11111111|11111111|11101110|10  3ffffba  [26]
    (  1)  |11111111|11111111|11101110|11  3ffffbb  [26]
```

The new *huffman-gen.py* supports both formats.