Added ShuffleInplace implementation to Network's Worker source

[GuilhermeRossato]

This PR solves this issue. The problem was that the Worker did not have the shuffleInplace function implemented.

To replicate the error before this commit try to train a network asyncronously with shuffle: true in config, like the following:

    trainer.trainAsync(trainingSets[channelId], {
        iterations: 2500,
        log: 250,
        rate: 0.01,
        error: 0.01,
        shuffle: true,
        cost: Trainer.cost.CROSS_ENTROPY
    })

Both npm run test and npm run build worked after this alteration locally, but I don't know how to make a failing/suceeding test with this stack, if someone does then feel free to replace this pull request entirely. Tested locally with the built /dist/synaptic.js file on a project and validated it fixes the issue too.