add lists type for `Keys`
changed `proplists:get_value/2` to `lists:keyfind/3` as possible
Merge pull request #11 from redink/master

add lists type for `Keys`

You can now specify a path into an EJSON object using either a tuple or a list. The following are now both accepted and equivalent:

```
ej:get({"a", "b"}, Obj),

ej:get(["a", "b"], Obj),

```