Throw error for non-valid keyword arguments in `fetch`

[eywalker]

Currently, when you invoke fetch with any unsupported keyword arguments (eg. rel.fetch(abcdefg=0)), the argument gets ignored silently. Although this may appear harmful at first, this makes detecting misspelled key word argument extremely difficult, leading to very difficult to spot bug in the code. When user passes in keyword arguments that are not explicitly supported by fetch (e.g. order_by or limit), then fetch should throw an error to notify the user.

[dimitri-yatsenko]

Fixed in #377