ci(travis.yml): added node versions

[coveralls]

Pull Request Test Coverage Report for Build 348

• 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 97.207%

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Totals
Change from base Build 342:	0.0%
Covered Lines:	1104
Relevant Lines:	1115

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💛 - Coveralls

[qiwibot]

:tada: This PR is included in version 2.4.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: