Highly requested dark theme

[mrkevinlin]

Hello, I have been testing implementing a dark theme on a separate branch.

http://imgur.com/a/nHP2k
Here's what it looks like so far.

There's simply a toggle (http://imgur.com/a/DgbTo) in the options to trigger it.

The colors can be adjusted, I just used some Google-suggested blue-gray material palettes to fill in the colors just to see how it would look. Any suggestions are welcome.

[tommyent]

Pretty close to what I've used in the past. I never got around to finishing it though.

[joaomgcd]

Looks good to me :D