Refactor handling settings

[stiffneckjim]

From review of #3 by @sfkleach:
The bottom of load_imdb.py has a if name == "main": clause. A really good rule is to never declare any variables in this section. This rule works to prevent awkward clashes and as a rule-of-thumb that it has got too big. The arguments are unpacked from a namespace into the global variable SETTINGS, which is a dict. My suggestion is firstly, how about make SETTINGS a namespace and then do SETTINGS = parser.parse_args()?

And I would be tempted to do away with a global SETTINGS by adding a class LoadIMDB: and stuffing all the methods into it. And then the global SETTINGS becomes an ordinary instance variable.