piscem v0.6.0

This version fixes an issue in the streaming canonical query class that is used to speed up index search for streaming queries. There were specific variables tracking state that were not always properly reset. As a result, a small number of queries could return invalid results (usually causing the corresponding reads not to map). This commit addresses this issue. The effect was quite rare (occurring in ~0.01-0.02% of reads), but the streaming query results now always match the results one would get without using the streaming optimization.