fix verbiage of environment setup subtitle in README

[nmwalsh]

No description provided.

[coveralls]

Pull Request Test Coverage Report for Build 926

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 48 unchanged lines in 14 files lost coverage.
• Overall coverage decreased (-0.5%) to 86.923%

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Files with Coverage Reduction	New Missed Lines	%
datmo/cli/command/base.py	1	92.96%
datmo/snapshot.py	1	83.49%
datmo/core/controller/file/driver/local.py	2	91.92%
datmo/cli/command/datmo_command.py	2	100.0%
datmo/core/util/i18n.py	2	100.0%
datmo/cli/command/run.py	2	81.5%
datmo/core/controller/code/driver/file.py	2	93.99%
datmo/cli/command/snapshot.py	2	100.0%
datmo/cli/command/session.py	2	95.7%
datmo/core/util/json_store.py	6	84.62%

Totals
Change from base Build 914:	-0.5%
Covered Lines:	3895
Relevant Lines:	4481

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💛 - Coveralls