For writing file diffs, try to read files with multiple encodings
For writing file diffs, try to read files with multiple encodings

When calculating file diffs, we try to read files with both utf-8,
and latin-1 encoding. These are the default encodings of python 3 and
python 3.

If the file can't be opened using one of those, a warning is issued.

Refs #121

recipy/recipy,recipy/recipy