Add unit test for the expected behavior described in issue #111

The unit test fails: when a paragraph is indented with less than 4 spaces
after a list, it should not be considered part of the last item of the list.
Only include paragraph with indent of 4+ spaces or a tab in a list item

I reverted to the code in the original project [1] for the detection of
whether a paragraph separated from a list item by a space should be
included in a list item.

[1] "Joining only indented stuff after empty lines"
in parse_listitem
in markdown.c
in faelys/libsoldout
https://github.com/faelys/libsoldout/blob/e106f0d74a03fb5edbebe11ce4b46eef7f575456/markdown.c#L1145
Add entry in change log for correction of issue #111
Merge pull request #317 from eric-brechemier/issue111

Conflicts:
	CHANGELOG.md
Fix the test provided in #317