Set title and revision using command line arguments instead of relying on STDIN

Right now, to create or update a task, we need to push JSON through it from STDIN. That’s cool and all, but it’d be nice to be able to write:

```
wlist inbox:create -t "Make me a smoothie!"
```

or

```
list task:update -t "Make that a cappuccino!" -r 1
```
