Read and write with `flowio`

[gegnew]

https://github.com/whitews/FlowIO

The python toolkit can't currently save an FCSFile resource to file (FCS format ) other than by downloading it directly from CellEngine (either through fcs_file.get_events or apiclient.download_fcs_file). It can't serialize the resource to an FCS file after making local modifications to it, right? Olivier is currently using the toolkit to make modifications to an FCS file and to save it back, using FlowKit package, but it's not super efficient and drops file-internal compensation matrix

[zbjornson]

Commented on the PR before seeing the comment here. That's correct. We need to be able to modify header values and maybe have some concept of a "local file" (one that isn't uploaded yet to CellEngine). Can work on designing the interface for this soon.