Input Range addition to associative arrays

[Phil Lavoie]

I tested your code and it seems to work correctly. However, what 
I find troubling is that I would never have thought of trying 
this out. This is because those two properties are said to return 
DELEGATES, according to this page: 
http://dlang.org/hash-map.html, but it does not seem to be 
correct. Now, I had a look at those properties' implementation 
and found out that they, in fact, return ranges, which 
contradicts documentation :(. I think it is safe to assume that  
both byValue and byKey return results in the same order, given 
that they use the same underlying range struct for popFront() and 
empty(). Thank you for pointing this out.