Taskwarrior 2.5.3 support

[vrusinov]

All tests pass and anecdotally everything seems to work for my scripts.

I'm not proud about some of the solutions, but hey - at least I can add tasks again.

Incorporates work by @EdwardBetts and joins together / obsoletes following pull requests:

• https://github.com/ralphbean/taskw/pull/141
• https://github.com/ralphbean/taskw/pull/142
• https://github.com/ralphbean/taskw/pull/143

And partially https://github.com/ralphbean/taskw/pull/139

[ralphbean]

@vrusinov @EdwardBetts thanks so much! Merging.