Fix vendor-related issue when using termbox types

[mocheryl]

Consider the following code:

package main

import (
    "github.com/nsf/termbox-go"
    g "github.com/quantum/gonsole"
)

func main() {
    app := g.NewApp()
    app.CloseKey = termbox.KeyCtrlQ

    app.Run()
}

It will not compile outside of gonsole directory because the termbox
type used here does not match the one used in the vendor directory.

According to some discussions I found, such behavior should be
restricted to main applications only. Libraries in this case should
either un-vendor the package or wrap all the exported types.