Usage:
======

Wrap your for loop in an extra scope with a progressbar, like this:

	{	// extra scope
		Progressbar p(std::cout);
		for(i = 0; i < 1000; ++i){
			...
			p.show(i, 999);
		}
	}	// end extra scope (destructor of Progressbar will be used).

You can give extra information to show in the constructor:
`Progressbar p(stream, "prefix", "Start message", " End message");`
this will look like:

	Start message
	prefix [===============>               ]
	End message

You may leave these things empty (`""`).

NOTE: the width of the bar (incl. prefix) is fixed ATM.
NOTE: pass the maximum-value to the function show, not the bound of the for-loop (this way the function also works nicely for floating types)