In ascii.read(), recognize list containing a newline

The `BaseInputter` class tries to detect whether the input is a file
object, filename, or iterable. However it can be fooled into thinking
that the input is a filename if it is a list of strings, one of which is
a newline.
Add unit test
Add changelog entry
Merge pull request #2648 from lpsinger/read_ascii_list_with_newline

In ascii.read(), recognize list containing a newline