Add link to Featuretools Time Series guide back into Daily Temperature 2 - Featuretools Solution notebook

The following sentence was not included in the second markdown cell because the Featuretools Time Series Guide was not yet completed

> A full explanation of how these terms are used can be found in [Featuretools' Time Series Guide]().

Once https://github.com/alteryx/featuretools/pull/1896 is merged in (and featuretools released?), we should add this link back in.