WIP: Add coverage steps to rust workflow; remove travis

[notquiteamonad]

Closes #46

[notquiteamonad]

Try switching to https://github.com/marketplace/actions/coveralls-github-action

[github-actions[bot]]

Pull Request Test Coverage Report for Build 5b6735253b564831307b8f9343b87abb57d6c520-PR-53

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 170 unchanged lines in 5 files lost coverage.
• Overall coverage decreased (-49.1%) to 50.657%

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Files with Coverage Reduction	New Missed Lines	%
src/date_time_tuple.rs	6	48.65%
src/date_utils.rs	18	50.0%
src/date_tuple.rs	19	59.06%
src/month_tuple.rs	26	50.45%
src/time_tuple.rs	101	43.34%
<!--	Total:	170		-->

Totals
Change from base Build 229:	-49.1%
Covered Lines:	523
Relevant Lines:	694

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💛 - Coveralls

[notquiteamonad]

Replaced by #54