Reword part of Readme about sanity checks

[krayzpipes]

This just sounds bad:

Sanity:
This is the algorithm to use with this filter in order to validate the data is really what you're looking for. For example, 16 digits might just be a random number and not a credit card. Putting the numbers through the luhn algorithm will validate they could potentially be an account number and reduce false positives.
You can also pass through a list of strings that represent algorithms as long as the algorithm exists in the library. If not, please add it and make a pull request!