Fixed problem with parameter modified at QueryingMethods

  Fixes #40 Keen query modifes options hash

### Overview
Most of the Query Method receive a params hash that should be added to the request. But, after query ended, the params have been modified(escape params and add others values).

**Example:**
```ruby
 options = {timeframe: {start: "2014-03-3", end:"2014-04-03"}}
 Keen.count 'a', options
 puts options
 {:timeframe=>"{\"start\":\"2014-03-3\",\"end\":\"2014-04-03\"}", :event_collection=>"a"}
```
### Issue
References and values and values that are references [(explained here)](http://stackoverflow.com/questions/22827566/ruby-parameters-by-reference-or-by-value/22827949#22827949)

### Solution 
Create a clone for params called ``query_parmas`` (according with the preprocess_params result)

New results:
```ruby
 options = {timeframe: {start: "2014-03-3", end:"2014-04-03"}}
 Keen.count 'a', options
 puts options
 {timeframe: {start: "2014-03-3", end:"2014-04-03"}}
```