ch10: add missing liftA2 in one of the examples

[eush77]

The first example in the Laws section of chapter 10 is not correct:

require('./support');
var Task = require('data.task');
var _ = require('ramda');


var tOfM = _.compose(Task.of, Maybe.of);

liftA2(_.concat, tOfM('Rainy Days and Mondays'), tOfM(' always get me down'))
  .fork(console.log, console.log);

$ node example
            throw new TypeError('can\'t concat ' + typeof set1);
            ^

TypeError: can't concat object

Instead, _.concat needs to be lifted into Maybe type:

var tOfM = _.compose(Task.of, Maybe.of);

liftA2(liftA2(_.concat), tOfM('Rainy Days and Mondays'), tOfM(' always get me down'))
  .fork(console.log, console.log);

$ node example
Maybe(Rainy Days and Mondays always get me down)

This is by the way a nice example of liftA2 being partially applied (as discussed earlier in this chapter).

[KtorZ]

Indeed!