Added ColorOuput to Config

ColorOutput controls color output to console

On windows command shell doesn't support color.
Usage (example from readme):
```
package main

import (
    "github.com/xyproto/web"
)

func hello(val string) string { return "hello " + val } 

func main() {
    // suppress terminal color output, default true
    web.Config.ColorOutput = false 
    web.Get("/(.*)", hello)
    web.Run("0.0.0.0:9999")
}
```