added max_stop to SequentialRangeMixin and a (trivial) implementation for SequentialRange
added BufferType to the infi.instruct.buffer imports
Instruct exceptions will now include the resolved references, making it easier to see why an error occurred
added some explanation on how total_size in unpack works and not overriding encapsulation of unpack_absolute_position_ref
using deref and not evaluate in FieldUnpackerReference, fixing a bug that caused unpack to be called _way_ too many times and slow down unpacking by x4.
Finished release v0.6.17.