Fixing URI error on installation

[aeanez]

When executing:

$ php vendor/kenjis/ci-phpunit-test/install.php --from-composer

The following error message is shown:

PHP Fatal error:  Uncaught UnexpectedValueException: RecursiveDirectoryIterator::__construct(application/application/tests/_ci_phpunit_test): failed to open dir: No such file or directory in /home/vagrant/test/vendor/kenjis/ci-phpunit-test/lib/Installer.php:214
Stack trace:
#0 /home/vagrant/test/vendor/kenjis/ci-phpunit-test/lib/Installer.php(214): RecursiveDirectoryIterator->__construct()
#1 /home/vagrant/test/vendor/kenjis/ci-phpunit-test/lib/Installer.php(99): Installer->recursiveUnlink()
#2 /home/vagrant/test/vendor/kenjis/ci-phpunit-test/install.php(14): Installer->install()
#3 {main}
  thrown in /home/vagrant/test/vendor/kenjis/ci-phpunit-test/lib/Installer.php on line 214

This was tested either in Debian 9 and Windows with different CI versions.

This pull request aims to solve this situation.

[coveralls]

Coverage remained the same at 70.104% when pulling 6840917 on aeanez:3.x into 214713b on kenjis:3.x.

[kenjis]

@aeanez Thank you!