Add MSE measure next to each analysis

[jeff1evesque]

We need to add a MSE measure for our ARIMA and LSTM predictors. Furthermore, any additional enhancements will be made as necessary.

[jeff1evesque]

We need to fix the ARIMA plot. Specifically, the original self.history before additional elements are appended, needs to be plotted:

        actuals, predicted, rolling, differences = [], [], [], []
        self.history = self.df_train[self.normalize_key].tolist()