Acknowledgments, automatically fetch contributors

This updates the acknowledgments with a more modern perspective. This
uses github4s to fetch all contributors for the following projects:

- ucb-bar/chisel2-deprecated
- freechipsproject/chisel3
- freechipsproject/firrtl
- freechipsproject/chisel-testers
- freechipsproject/treadle
- freechipsproject/diagrammer

Papers directly involving Chisel/FIRRTL and gel are added as well as
citation pleas.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>