Merge pull request #20 from EdFuentetaja/master

Added decoding and error correction on the NID fields: NAC and DUID.
Add itpp as a requirement in readme
Merge pull request #22 from EdFuentetaja/master

Added support for error correction in P25 HDU data.
Use gtest for golay24 and reed-solomon tests
Update samples
Added a few comments, fixed ortography and some other cosmetic changes.
Merge branch 'master' of https://github.com/szechyjs/dsd.git
Added error correction to the metadata of LDU1 and LDU2.
Refactored implementation of p25p1_ldu1.c and p25p1_ldu2.c. There are less duplicities now and hopefully is easier to read and maintain.
Added a unit test for the Hamming algorithm.