Bug 16685 [QA Followup] - Use Path::Tiny::slurp instead of File::Slurp

Bug 16685 [QA Followup] - Use Path::Tiny::slurp instead of File::Slurp

Path::Tiny::slurp is considered better to use than File::Slurp.

RM Note: The package version in wheezy is too old, the package version
         in jessie is just fine and should be added to the community
         repo if wheezy will be supported for the coming release.

Signed-off-by: Aleisha Amohia <aleishaamohia@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>