0.6.0b1

This is the first beta release of the 0.6 series.

The main change with respect to the v0.5 series is the update from BirdVoxClassify v0.2 to v0.3. The species classifier is now "flat multitask" by default and includes hierarchical consistency. Furthermore, the order "Passeriforme" is now spelled in the plural: "Passeriformes". We have added various encodings for species: English name, scientific (Latin) name, and 4-letter code (#85). The "other" class is represented as an empty string. Lastly, we have truncated the number of digits of confidence in the checklist (#86).