Update to TAP v14

[jenstroeger]

It probably doesn’t matter for the majority of consumers, but perhaps switching to TAP spec v14 might make sense? It seems to be more detailed and better defined, too.

[mblayman]

Support for this will need to happen in tappy first. python-tap/tappy#123

Both of these projects are currently in a maintenance mode because I don't have time to work on them.