Test enhancement

[peter279k]

Changed log

• Remove --configuration option from phpunit command during Travis CI build because this option cannot be added when the phpunit.xml path is same as execution command path.
• Add php-7.3 test in Travis CI build.
• Replace try...catch block with expectException and expectExceptionMessage methods.
• Replace 'Exception' with \Exception::class for all expectException method.
• Using assertCount method to assert whether the array length is same as expected count.
• Using assertArrayHasKey to assert the specific key is existed in $result array.
• Using assertArrayNotHasKey to assert the specific key is not existed in $result array.

[iranianpep]

Thanks @peter279k. I bumped up the release number.