Add .to_s guard methods to circumvent errors

Apparently, due to my current harvester implementation arrays with
strings representing numbers are converted into integers. It is not
supposed to be this way, but for a more robust code I am dealing with
this issue by adding .to_s guard methods.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Patch a series of text manipulation problems

There are still many problems, that need to be solved in a more cleaner
way. For now I have patched these issues until more appear.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>