Remove normalisation from remaining mappers

[hollsk]

As discussed in #55 and #58. Data is normalised in three mappers (statsd, statsd-npg, waterfall), which removes a bunch data from each payload. statsd is the default, so most users are probably going to use that first - unless they can work out from the documentation what's going on, they're going to be confused.

We should remove the normalisation step from the remaining mappers, probably prioritising statsd.