Add fail notification hooks before tasks run

[juriejan]

This will resolve #39 where running a grunt-contrib-watch task with spawn:false would not produce notifications on failure.

I'm not entirely sure if this is the best solution, but it's what I could come up with in a limited amount of time.

I see that there are sample watch tasks in the Grunt configuration file, but I didn't see that they where used in any tests. Perhaps someone can help set these up with some tests. Will see if I can get to it myself when I have time.

[dylang]

Interesting, I look forward to trying your solution out.

[juriejan]

I'm not sure if this will keep adding more hooks to the grunt.fail methods each time a task runs, but on a quick test, it seemed not to.

[juriejan]

This was also tested with the latest grunt-contrib-watch at the time (0.5.3).

[dylang]

I fixed this a different way:
a29474d

[juriejan]

Awesome! Looks good.