Recognize path when validating

Fixes #11. After changing the directory to the root directory specified,
we want to call lstat on a relative path, instead of joining the
full root path with the file name.

Signed-off-by: Stephen Chung <schung@redhat.com>

check.go

@@ -50,8 +50,7 @@ func Check(root string, dh *DirectoryHierarchy, keywords []string) (*Result, err
 				creator.curSet = nil
 			}
 		case RelativeType, FullType:
-			filename := filepath.Join(root, e.Path())
-			info, err := os.Lstat(filename)
+			info, err := os.Lstat(e.Path())
 			if err != nil {
 				return nil, err
 			}