Fix compatibility issues with Perl 5.8

Fix compatibility issues with Perl 5.8 by modifying $token->tokenize() to
use the pack() format specifier 'C' rather than 'W'

Other changes:

    * Remove usage of Carp from ::Token

    * Prevent a call to Carp->import()

    * Update module authorship, copyright years, and replace README with file
      README.md as generated from pod2markdown

    * Add Changes file to improve kwalitee score