Return predict result to user

[syt123450]

When user doing predict in tensorspace, tensorspace would pass predict result to user.

[syt123450]

two steps:

• refactor prediction process with predictor
• add callback for predictor

[syt123450]

Now user can get predict result from callback, use like this:

model.predict(data, function(predictResult) {
    console.log(predictResult);
});