v3.0.0

• adapted "black" code formatter for this repository (#262)
• BREAKING: dropped support for Python 3.3 (#242)
• BREAKING: changed order of precedence when evaluating configuration (#255, #261)
• BREAKING: changed default value of span_frames_min_duration setting
  from -1 (always collect) to 5 (only collect for spans longer than 5 ms) (#243)
• added instrumentation for pymssql (#241)
• added instrumentation for pyodbc (#238)