* Add support for declaring arguments as repeatable
If the usage of the argument includes the phrase "Can be repeated.",
the corresponding arg_ variable will be an array containing one element
per instance of the argument.
* Add example and test for using repeated parameters
* Add example and test for using repeated flags
templater.sh now escapes the delimiter it uses for its sed magic within
the environment variable content.
the associated test uses a properly cleaned up temporary file instead of
explicitly rm-ing its own mess.
If the description of an option contains the single word sentence
'Required.' it is understood as a required argument and automatic
validation will make sure that it is set or end the script by calling
help.
Alternatively, if the argument within the __usage string is {arg}
instead of [arg] it is understood as a required argument and automatic
validation will make sure that it is set or end the script by calling
help (even if 'Required.' is not in the description).
Closes#22
