"Could not load module libhdf5" when installed by Homebrew.jl on OS X

You use BinDeps to install libhdf5.  On OS X, this uses Homebrew.jl.  Unfortunately, Homebrew's lib path isn't automatically added to the DL_LOAD_PATH.

This simple patch adds Homebrew's lib to DL_LOAD_PATH on OS X before the `dlopen`.  Not sure if there's a better way here, but this works.