Fix attr access for empty arrays

Note: this will crash until https://github.com/ContinuumIO/libdynd/pull/89 is merged
I've been using {} around the body of all if and if/else statements.

Also, check out clang-format to automatically format code in your text editor with a keystroke. It's pretty sweet and I've put .clang-format files in both dynd-python and libdynd.