Fix Javadoc warning for PosixFileAttributeView

PosixFileAttributeView was referenced in the Javadoc, but
the class was not imported which caused this build warning:

warning - Tag @see: reference not found: PosixFileAttributeView#name()
Merge pull request #54 from spotify/rculbertson/fix-javadoc-warning

Fix Javadoc warning for PosixFileAttributeView