__init__.py:
- replaced _cypherQuery() and _threadedQuery() methods with new
threading-based Results class, which uses the new
py2neo.neo4j.CypherQuery.stream() method. This also obviates the
ordering behavior of the _assemblePattern() and results() Query methods.
- limits are now hard-coded in _assemblePattern()
- added missing music21 namespaces
- edited docs

musicNetServer.py:
- prepareQuery() now creates a Results object and stores it for the
token
- generate_results() now gets data from Results.next()

previews.py:
- incoming queue is emptied on startup