Add ability to start tasks

[paanvaannd]

$ task-web --version
rack 1.3
sinatra 2.0.5
vegas 0.1.11

I use Timewarrior to log time spent on Taskwarrior tasks automatically with the provided Taskwarrior hook. There is also an article I've followed to implement automatic Gnome Pomodoro interactions in conjunction with Timewarrior and Taskwarrior.

The only interaction this requires on my part is to start a task using Taskwarrior. Therefore, an addition of the task <task_ID> start function in taskwarrior-web would be much appreciated.

[tdelcourt]

It would be nice to start tasks from the web interface, and that started tasks would/could be coloured differently, as in taskwarrior.
I start tasks so that it is clear in the todo-list what I'm currently working on (as some tasks take some time to perform, so I usually have several ongoing in parallel; maybe not the best set-up but it works for me).