Created a flag for specifying dark themes.

No implementation yet, but progress.

Ref #100
Reverted changes on a links in the CSS file.

I accidently set the new colour to #AAA, which
in turn, set every link, including logs, ....,
to be #AAA instead of #333. I could easily set
more things to have #AAA as their colour,  but
in doing that, it'd mean more lines of code.
Renamed style.css to light.css.

Then CSS handler in serve.go makes sure to serve
whichever CSS file we specify as the main one to
serve. It only will serve one file. Currently it
only serves light.css. dark.css is not yet made.

Ref #100
Added dark.css as an option (use flag dark).

The CSS still needs to be done, so I wouldn't say that
it's done yet, but that it'll be done soon.

Ref #100
Got *fDark working correctly.

I'm not sure exactly what the error was in serving two
different files as style.css. I mean, it only served 1
file as style.css, but after each time it would get re-
loaded with a differnt type of style sheet, it wouldn't
correctly do what it was supposed to. The way it is now
works fine though. Almost done, now just dark.css.

Ref #100
Styling dark.css

Ref #100
More changes to dark.css

Ref #100