Add "<3" constraint to hashie gem.

This appears to solve the problem of a Hashie version resulting in errors such as this one:

```
/Users/kbennett/.rvm/gems/ruby-1.9.3-p448@jiradox/gems/hashie-3.0.0/lib/hashie/trash.rb:80:in `property_exists?': The property 'expand' is not defined for this Trash. (NoMethodError)
	from /Users/kbennett/.rvm/gems/ruby-1.9.3-p448@jiradox/gems/hashie-3.0.0/lib/hashie/trash.rb:49:in `[]='
```