build

Add IO conversion methods #499

Job	Run time
build (ubuntu-latest)	59s
build (windows-latest)	1m 48s
test (macos-latest, beta)	48s
test (macos-latest, nightly)	52s
build-other (wasm32-unknown-unknown, beta)	1m 11s
test (ubuntu-latest, beta)	32s
build-other (wasm32-unknown-unknown, nightly)	1m 38s
test (ubuntu-latest, nightly)	32s
test (windows-latest, beta)	1m 7s
build-other (wasm32-wasi, beta)	48s
test (windows-latest, nightly)	50s
build-other (wasm32-wasi, nightly)	1m 10s
build-other (x86_64-unknown-redox, beta)	1m 7s
build-other (x86_64-unknown-redox, nightly)	52s
build-other (x86_64-fortanix-unknown-sgx, nightly)	1m 26s
	15m 40s

Provide feedback