[Refactor] combine `sed -e` invocations/arguments #288

Job	Run time
tests (install_script, bash)	1m 41s
tests (sourcing, sh)	45s
tests (sourcing, bash)	47s
tests (sourcing, dash)	44s
tests (sourcing, zsh)	1m 5s
tests (slow, sh)	3m 15s
tests (slow, bash)	3m 19s
tests (slow, dash)	3m 9s
tests (slow, zsh)	5m 13s
tests (installation_iojs, sh)	59s
tests (installation_iojs, bash)	2m 1s
tests (installation_iojs, dash)	1m 1s
tests (installation_iojs, zsh)	1m 19s
all test suites, all shells	1s
	25m 19s

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