The review of std.hash package

[David]

Is the API already set in stone?

Using .start and .finish, feels like the use of OpenSSL. Why not making 
a Hash object not "restartable" (since e.g. MD5.start() sets `this` just 
to MD5.init) and making finish private and implementing a digest and 
hexdigest property which calls finish and returns an ubyte[] array (or 
string for hexdigest), this would also eliminate the need of the 
`digest` wrapper (e.g. you can mixin these properties with template 
mixins, so no code duplication)

Also I am not sure if we want to use `hash.put` instead of `hash.update` 
(which is used by python and openssl). But that's just a minor point 
(e.g. perl uses .add)

Furthermore, I don't like the `sha1Of` and `md5Of` etc. functions, why 
not having a static method? e.g. MD5.hexdigest("input"), which returns 
the hexdigest and not a MD5 object.

One more thing, `.reset` does the same as `start`? If so, why do both 
exist? (I also find the examples quite confusing, why do you want to 
reset the hash onject? I would documentate the function but wouldn't use 
it in the examples)

Well, that's it from my side :)