Remove special columns from namedtuple in nate class

[Pierson Browne]

Currently, all of the 'columns' passed into a nate object are stored in self.data, which can be very memory-inefficient.

If we keep the special columns (text, time, ID) separate, and package all of the non-special columns into the self.data object, we'll get the best of both worlds (easy compartmentalization in namespaces, memory efficiency)

Not critical unless we encounter memory bottlenecks.