Make monochrome more consistent and prettier

- `fringe` bg is black. I think the white one look ugly and distracting.
- `region` is now gray to discriminate with point color. It also eases the eyes when a large region is selected.
- `helm-match` is now black and white to make it consistent with the rest of `helm`.
- I also added support for Magit to make it usable in GUI and terminal. When a hunk is selected, the hunk is bold instead of activating region on hunk which is difficult to read.