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)
`~~` is the smart maching operation only available in perl 5.10+. I'd like this script compatible with older perls like 5.6.

BTW, it seems that you should really use a hash table here for "bracket_levels" instead of an array.