Tracking issue for num-rational 0.3 #65
Description
- Update to MSRV 1.31, 2018 edition #66: Update MSRV to 1.31 and num-bigint 0.3
- Convert to 2018 edition too
- add more formatting traits #56: add more formatting traits -- might want constraint changes
Other PRs and issues may be included too, but these are the ones that impact compatibility.