Atom encoding

Yet another patch from the opscode guys. While here, provide a test case which fails before and succeeds after the application of their change.

I think it is rather sane if you can encode an atom name as a value directly into the MySQL driver. One would expect that the atom can be encoded like this.

There is one caveat though: In the future, atoms are likely to contain unicode data. We probably need a way to encode this later on via atom_to_binary(X, utf8) and so on. But I say, lets get this in and then handle those problems later, depending on how all our encoding woes pans out. One can always do the encoding to a binary oneself if it proves to be a problem, this is just a nice convenience.