Added IOManager._display_errors().

The method is a one-line wrapper around IOManager._display().

The method sets capitalize=False.

The method serves to document calls to display that should dump a stacktrace.

With vanilla _display():

Traceback (most recent call last):
File "/Users/trevorbaca/Documents/scores/krummzeit/segments/segment_a/__illustrate_segment__.py", line 4, in <module>
From definition import segment_maker
File "/Users/trevorbaca/Documents/scores/krummzeit/segments/segment_a/definition.py", line 13, in <module>
Time_signatures=time_signatures,
File "/Users/trevorbaca/Documents/scores/krummzeit/makers/SegmentMaker.py", line 20, in __init__
Self._initialize_time_signatures(time_signatures)
AttributeError: 'SegmentMaker' object has no attribute '_initialize_time_signatures'

With _display_errors():

Traceback (most recent call last):
File "/Users/trevorbaca/Documents/scores/krummzeit/segments/segment_a/__illustrate_segment__.py", line 4, in <module>
from definition import segment_maker
File "/Users/trevorbaca/Documents/scores/krummzeit/segments/segment_a/definition.py", line 13, in <module>
time_signatures=time_signatures,
File "/Users/trevorbaca/Documents/scores/krummzeit/makers/SegmentMaker.py", line 20, in __init__
self._initialize_time_signatures(time_signatures)
AttributeError: 'SegmentMaker' object has no attribute '_initialize_time_signatures'

Note that lines like 'Self._initialize...' in the old forumation are incorrect.