Unit tests return ERROR or FAIL about gaia

[alastair]

It seems that many of these are failing to load files. However, there's a test/unittest/data/dataset_small.tar.bz2 file. It's got a folder in it called yamaha_small, but it needs to be renamed to dataset_small. We should uncompress it. We can consider doing like we do with essentia, having a git submodule for test files, instead of this tarball.

After doing this, my test results are:

Ran 99 tests in 31.176s

FAILED (failures=1, errors=11)

[dbogdanov]

We can also consider updating the tests to use a small set of AcousticBrainz descriptor files. I am thinking to use those for a tutorial (#106). The nice thing is that the songs will be linked to AcousticBrainz and Youtube videos.