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A famous set of computer problems involve verbal arithmetic.  In these problems,
you are given equations of words like:

	  send
	+ more
	------
	 money

or:

	  forty
	    ten
	+   ten
	-------
	  sixty

The goal is to find a single digit for each letter that makes the equation true.
Normal rules of number construction apply, so the first digit of a multi-digit
number should be nonzero and each letter represents a different digit.

This week's quiz is to build a program that reads in equations and outputs
solutions.  You can decide how complex of an equation you want to support, with
the examples above being the minimum implementation.

Here's a solution you can test against:

	$ ruby verbal_arithmetic.rb 'send+more=money'
	s: 9
	e: 5
	n: 6
	d: 7
	m: 1
	o: 0
	r: 8
	y: 2