Only :colo pablo if on Windows non-GUI

I've used the default colorscheme on Ubuntu's terminal and find it acceptable. On Windows, however, I find the default scheme at times unreadable. The colorscheme pablo line is intended to change to what I see as a more sensible colorscheme for Windows's terminal.

Of course, this doesn't apply to gVim, where I still prefer Solarized. I might look into setting that up for TTY as well.