FormatSpime use of map breaks 2to3

[wcpettus]

This doesn't work in python3:
https://github.com/project8/dragonfly/blob/develop/dragonfly/implementations/spime_endpoints.py#L170
(well, it doesn't work when you call the [0] element in a couple lines)

Error is:
got a: 'map' object is not subscriptable

[laroque]

Problem is that the map function returns an iterator of type map in python 3.

Solution options are: https://python-future.org/compatible_idioms.html#map

I think probably 4 is best/most consistent with what we've been doing elsewhere