feature: added support for command-line arguments parsing

* Adding support for command-line arguments parsing
* Adding support for multiple directories to the search paths for Lua libraries
* Using Getopt::Long instead of Getopt::Std
* Adding a new test scaffold
* Adding support for specifying the nginx path (this option might be removed in the future)
BTW This new `--nginx=PATH` feature was not mentioned in your commit log messages.