Only run the load_colors() function if we are showing color

[petdance]

No point in loading a module (two on Windows) if the user does not need the functionality.

[petdance]

Also, if the modules don't load correctly, turn off $opt->{color}.

[petdance]

There's a redundant check that needs to be addressed.

    if ( !defined($opt_color) && !$opt_g ) { 
        my $windows_color = 1;
        if ( $App::Ack::is_windows ) { 
            $windows_color = eval { require Win32::Console::ANSI; };
        }   
        $opt_color = !App::Ack::output_to_pipe() && $windows_color;
    }   

[petdance]

Specific case: There's no point in loading the color modules if we're piping to a file and therefore there is no color.