Test enhancement

[peter279k]

Changed log

• Add .cache file to let these files not be under Git version control.
• Add php-7.3 and php-7.4 version tests on Travis CI build.
• Using composer install command on Travis CI build because the composer.lock file is not under Git version control.

[coveralls]

Pull Request Test Coverage Report for Build 27

• 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 95.238%

---

Totals
Change from base Build 24:	0.0%
Covered Lines:	20
Relevant Lines:	21

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 26

• 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 95.238%

---

Totals
Change from base Build 24:	0.0%
Covered Lines:	20
Relevant Lines:	21

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 26

• 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 95.238%

---

Totals
Change from base Build 24:	0.0%
Covered Lines:	20
Relevant Lines:	21

---

💛 - Coveralls