* finally fix decoder leaks and de-synchronizations (thanks to piem)
* this also fixes bad variable encoder file lengths
* fix OGG and FLAC encoders (closes: 8)
* fix multi-channels streaming (closes: 13)
* add support for Pillow (closes: 12)
* temporally desactivate AAC and WebM encoders (need to add some limits for them)
* WARNING : we now need to add overwrite=True to encoder kwargs instances in order to overwrite the destination file, i.e. e=Mp3Encoder(path, overwrite=True)