Release 0.0.81

See #1149, release log:

• 8ecbc4d by @rultor: 0.0.82-SNAPSHOT
• c8f285d by @amihaiemil: Merge pull request #1148 from ...
• a8f2935 by @amihaiemil: Merge pull request #1147 from ...
• 0c524eb by @criske: Fixed bug where etag header wi...
• 4712150 by @criske: #1134 Added overloaded methods...

Released by Rultor 1.69.1, see build log