Test enhancement

[peter279k]

Changed log

• Add *.cache to let cached files avoid being under Git version control.
• The composer.lock is ignored on Git version control, it's fine to use composer install command on Travis CI build.
• Add php-7.3 and php-7.4 version tests on Travis CI build.
• Add EOF (the end of file) for some files.

[coveralls]

Pull Request Test Coverage Report for Build 5

• 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 100.0%

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Totals
Change from base Build 3:	0.0%
Covered Lines:	146
Relevant Lines:	146

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💛 - Coveralls