Suggested fix to broken attr behaviour

[robpre]

This is my fix for the bug/inconsistency mentioned in #667

[daffl]

This actually looks pretty good for 2.0.5 and doesn't seem to interfere with anything else.

/cc @justinbmeyer, @thecountofzero

[justinbmeyer]

Actually, I wasn't aware this code existed in the first place. It performs double reads for every attr call with a ".".

#257 and #269 and this commit are related: a80bd62

I'm not sure what to do as I'd prefer not to do double reads.

[andykant]

If there is a double read I think it's worthwhile for the consistency, although in my testing the amount of lookups in both cases was roughly the same.

Optimally you wouldn't have data organized like this in cases where the performance was an issue.