PosixFileNameComparator didn't sort same names with different cases right

For example "abc", "ABC", "aBc" was sorted incorrectly

Also same name with and without dot was not sorted correctly.

"aa" should be before ".aa", this case was not sorted
Merge pull request #71 from rbalent/compare-different-case

PosixFileNameComparator didn't sort same names with different cases right