Log Message:
py-ruamel-yaml: updated to 0.16.10

[0, 16, 10]:
- (auto) updated image references in README to sourceforge

[0, 16, 9]:
- update CHANGES

[0, 16, 8]:
- update requirements so that ruamel.yaml.clib is installed for 3.8,
  as it has become available (via manylinux builds)

[0, 16, 7]:
- fix typchecking issue on TaggedScalar
- fix error in dumping literal scalar in sequence with comments before element

[0, 16, 6]:
- fix empty string mapping key roundtripping with preservation of quotes as `? ''`
- fix incorrect state setting in class constructor
- adjust deprecation warning test for Hashable, as that no longer warns