Support for readSymbolicLink and fixing BlockInputStream#read 

While using this library to support unit tests, I encountered an infinite loop in BlockInputStream#skip which is fixed here. I think the code contained a loop by mistake.

Also, the implementation supported the creation, but not this API java.nio.file.spi.FileSystemProvider.readSymbolicLink(Path).
I added support for that by looking at the getFile implementation.

Added unit test to cover new code.

mvn test:
....
Results :

Tests run: 1629, Failures: 0, Errors: 0, Skipped: 7