fix validation type coercion for comparison queries in issue #7

[pablohirafuji]

Hey, the issue is only when comparing :text type fields. It does not happen when the field is :bigint or :timestamp because it does not pass through this validation:
defp coerced_value(value, :text) when not is_binary(value), do: to_string(value)

It was passing the list parameter directly to:
defp coerced_value(value, _), do: value
because it doesn't have a case that match when is_list on the coerced_value function. Only :text because lists are a not is_binary match.

[weixiyen]

Thank you for the fix! Will update to 0.2.1