Escape translations and interpolated values

We should always assume that translations and the interpolated values
that are placed into that translation are malicious. This PR will escape
any html within these by default. You may unescape interpolated values
using the `unescape` option.
Devil's advocate: Do we think that `whiteslitedKeys` is too long? It is 15 characters long as opposed to something like `escape` which is 6.