Transmission::Types: Numify numbers when coercing

Transmission is really picky on how the JSON is encoded, and if it
gets a numerical value encoded as a string it will simply no-op,
without reporting an error.
Initial unit tests for Transmission::Types
Initial set of unit tests for Transmission::Torrent
Transmission::Types: Type names come from RPC spec

The types named defined in Transmission::Types corresponds to the
types used in the transmission RPC specification. Mention this in
the POD.
Add *.tar.gz to .gitignore