Add GET parameter for specifying the query processor

Fix #188.

Signed-off-by: Don Naegely <naegelyd@gmail.com>
I see. Sounds good, thank you.

On Mon, Sep 15, 2014 at 3:44 PM, Don Naegely <notifications@github.com>
wrote:

>> @@ -99,8 +111,15 @@ def test_values_random(self):
>>          self.assertEqual(response.status_code, 200)
>>          self.assertEqual(len(json.loads(response.content)), 3)
>>  
>> +        # Trigger an exception by applying a query process which restricts
>> +        # the possible values to 1 while requesting 3. If the query processor
>> +        # arg is respected then an error will result.
>> +        self.assertRaises(
> This happens because [this line](https://github.com/cbmi/serrano/blob/master/serrano/resources/field/values.py#L71) in Serrano calls the `random` method on the `DataField` object which in turn calls `random.sample` on [this line](https://github.com/cbmi/avocado/blob/master/avocado/models.py#L667). `random.sample` throws the `ValueError` if the number of random items being requested is larger than the population being drawn from. I will update Serrano to account for this and update this PR.
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> https://github.com/cbmi/serrano/pull/192/files#r17564093