Create automated tests using BATS

[phil-davis]

This uses the Bash Automated Testing System at https://github.com/sstephenson/bats as a framework for testing this command line utility.

As a start, I have made:
a) command_params.bats - basic tests to see that each generic command option ( -h, -v etc) works
b) display_ipv4.bats - at first 3 tests to check the output for the 3 old-fashioned "classes" of IPv4 private space at their most basic, using CIDRs that match the "classes". When I made these, I found a little bug in the RFC reference number (see misc.c - the fix is required so that the tests will pass)
c) validate_address_ipv4.bats - check a lot of variations of things that are, or look a bit like, IPv4 addresses.
d) validate_address_ipv6.bats - check a lot of variations of things that are, or look a bit like, IPv6 addresses.

Since I have managed to find a first bug while writing tests, I will submit this PR for your consideration.

[phil-davis]

I started doing this because I am doing a SW Engineering course and wanted to make a demonstration of how test driven development (TDD) is useful in applications that are not OO.
Since I have a background in networks, routing, firewalls... this seemed a nice little utility where I already know and understand what the outputs should be like, and it can easily be tested using this BATS framework.
I am happy to add more tests, if you are happy with the using the BATS framework.

[troglobit]

Great work!

You're more than welcome to add more tests 😃 👍