Changed PWP::Encoding to PWP::SingleEncoding.
Merge pull request #4 from sergeyromanov/patch-2

Changed PWP::Encoding to PWP::SingleEncoding.
Relocated isa and asa constraints and made them available to UNIVERSAL.
Added tests and changes to ensure methods that modify their subject work as intended.
Added the output role to all data types.
Updated POD, README, and Makefile.
v0.33

 - Updated POD, README, and Makefile.
 - Added the output role to all data types.
 - Added tests and changes to ensure methods that modify their subject work
   as intended.
 - Relocated isa and asa constraints and made them available to UNIVERSAL.
 - Changed PWP::Encoding to PWP::SingleEncoding.