Fix find_by functions in Riak Store to work with different data types, not only binaries.

[cabol]

Currently, due to Riak store works with binaries inside, the find_by/5 function doesn't works well with values different than binaries in the conditions.

E.g.: if you have an integer field in your model, and you want to find all results that match with that field:

sumo:find_by(my_model, [{age, <<"10">>}]).

The idea is modify sumo_store_riak to allow work with different data types, as defined in the schema, E.g:

sumo:find_by(my_model, [{age, 10}]).

[harenson]

Already fixed.