declare warning on osx

Getting this:

```
./lib/shunt.sh: line 191: declare: -A: invalid option
declare: usage: declare [-afFirtx] [-p] [name[=value] ...]
```

on `Darwin 14.0.0 Darwin Kernel Version 14.0.0: Fri Sep 19 00:26:44 PDT 2014; root:xnu-2782.1.97~2/RELEASE_X86_64 x86_64`
