Changed back so that curl is used by default, however dig can be used
as a backup if curl is not installed on the system. Additionally took
my fear of code injection into account by sanitizing the remote input
through a regex.
Used shell built-in command -v to determine if dig is installed and if
it is, use it as default for getting the ip-address. Also made the use
of brackets consistent and updated the the way the data variable is
created before it is sent with curl to make it more readable in the
code.