Currency Normalization Primitive

As a user, I wish I could use Featuretools to normalize currency both spatially and temporally. It is common to convert currency to USD when comparing values from different currencies. It is also common to account for inflation when comparing currency values across time.

## Inflation

To account for inflation, there is already a [python library](https://github.com/palewire/cpi) that does this using the Consumer Price Index.

## Exhange Rates

There is also a [python library](https://github.com/MicroPyramid/forex-python) that contains historical foreign exchange info from 1999 onward.

#### Code Example

I'm unsure at this point, what the code would look like, but imagine if your dataframe had 3 columns `CurrencyType`, `Date`, and `Value`. The TransformPrimitive operation would by default convert the value from its currency at that datetime to its USD value today.