Merge pull request #68 from zcash/msrv-1.60 #285

Job	Run time
Bitrot check	1m 53s
Book tests	1m 21s
Code coverage	2m 44s
Intra-doc links	1m 44s
Rustfmt	14s
Test on ubuntu-latest with --all-features	2m 31s
Test on ubuntu-latest with --no-default-features	2m 38s
Test on windows-latest with --all-features	3m 6s
Test on windows-latest with --no-default-features	3m 37s
Test on macOS-latest with --all-features	3m 35s
Test on macOS-latest with --no-default-features	4m 8s
Check no-std target thumbv6m-none-eabi	1m 18s
Check no-std target wasm32-unknown-unknown	1m 17s
Check no-std target wasm32-wasi	1m 13s
Test on i686-unknown-linux-gnu with --all-features	2m 17s
Test on i686-unknown-linux-gnu with --no-default-features	2m 34s
	36m 10s

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