Added ability to change theme from command line arguments

[jamesofarrell]

Adds the ability to theme hangups from the command line and config file.
learnt how to use lint. this will pass the tests, sorry about the pull spam.

[tdryer]

Nice, thanks!

There's also #166 by @AshenDrops which instead allows adding colour schemes via separate files. We should consider which approach (or both?) is best to have.

[tdryer]

Can you also add the existing --col-scheme option to this group?

[tdryer]

If you run the changed files against pep8, it will point out a few other suggestions (I should add that to the automatic check as well).

[jamesofarrell]

I spotted #166 after I wrote most of the code but I decided that since this lets you override single values instead of the whole theme I would finish it anyway. It should just slot in next to JSON code with no issues as $166 loads more themes are start-up while this just lets you override values of the selected theme.

I’ll have a look at the other issues now and see what I can do.

[jamesofarrell]

Hopefully that should fix all the issues. Let me know if there is anything else.

[tdryer]

Last choice should be 256 instead of 265.

[jamesofarrell]

yes, yes it should be. Fixed now

[tdryer]

Thanks again!