v0.0.5

Fixed

• MS3Record.samprate consistently returns the rate in samples/second,
  and MS3Record.samprate_raw returns the record's raw value.
• Properly return None when MS3Record.sampletype is not set.

Added

• MS2Record.unpack_data() to decode sample payload after parsing.
• MS3Record.samprate_period_ns to return sample period in nanoseconds.
• MS3Record.samprate_period_seconds to return the period in seconds.