Appveyor CI build fails

[filfreire]

AppVeyor fails with:

[00:00:58] [WARNING] Rule 0: org.apache.maven.plugins.enforcer.AlwaysFail failed with message:
[00:00:58] You should use Unix-like or Mac OS to successfully build Rultor.
[00:00:58]                                                 With an other OS you are still able to check sources with the command:
[00:00:58]                                                 'mvn qulice:check -Pqulice'
[00:00:58] Always fails!

example: https://ci.appveyor.com/project/yegor256/rultor/build/1082

we should probably do these:

• disable appveyor integration and delete badge from documentation;
• mention in documentation that building on Windows env is not supported;

[filfreire]

@yegor256 fyi

[0crat]

@yegor256 please, pay attention to this issue