Add --color=[dark|light|16|bw] option

- dark:  the current default for 256-color terminal
- light: color scheme for 256-color terminal with light background
- 16:    the default color scheme for 16-color terminal (`+2`)
- bw:    no colors (`+c`)

src/terminal.go

@@ -105,7 +105,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		suppress:   true,
 		startChan:  make(chan bool, 1),
 		initFunc: func() {
-			C.Init(opts.Color, opts.Color256, opts.Black, opts.Mouse)
+			C.Init(opts.Theme, opts.Black, opts.Mouse)
 		}}
 }