increase speed of isInt() method

Regular expression is very slow actually. Sometimes we can't handle some situation without regexp but when we need to know that string has only numbers we can check it much faster than **preg_match()**

For example we can **is_numeric()**. It works much faster. 
Here is cool gif :)
![d8q08](https://cloud.githubusercontent.com/assets/910691/4694177/b610c97c-57bf-11e4-9476-f941a2a19e2b.gif)

First line (**test_without_regex**) is **is_numeric($data)**
Second line is **preg_match**
And last one is **(int)$data** and some additional **IFs**

So, I heard you want to build a fast cms. So I guess this pull request will help you.