Remove obsolete `version` field from compose spec

[sajith]

Resolves #278.

[coveralls]

Pull Request Test Coverage Report for Build 9425178656

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 52.132%

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Totals
Change from base Build 9319526474:	0.0%
Covered Lines:	738
Relevant Lines:	1446

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💛 - Coveralls