Update to 0.31
    
    - New upstream release 0.31:
      - Optimization: stringify variables passed to canonpath
      - Optimization: Use internal guts when constructing Dirs from Dirs, instead
        of concatenating and splitting them again with File::Spec
      - Fix grammar error in docs
      - Implement a 'split' parameter for the slurp() method
      - In docs, replace unicode MINUS SIGN with ascii HYPHEN-MINUS
    - BR: perl(Scalar::Util)