Fix: escape element id attribute before using it as selector

Hi,

this PR solves problem, when input's id attribute contains characters which have to be escaped in order to plugin to work. Similar to [this pull request] (https://github.com/arthurgouveia/prettyCheckable/pull/95), but now also escaping other characters than `.`.

So cases like:
```
<label for=":'(">man</label>
<input id=":'(" name="gender" type="radio">
<label for=")$#!~">woman</label>
<input id=")$#!~" name="gender" type="radio">

<label for="flat.flat">Pretty checkbox 2</label>
<input class="pretty" id="flat.flat" type="checkbox">

<label for="asd!*">Pretty checkbox 3</label>
<input class="pretty" id="asd!*" type="checkbox">

<label for="!@##$%^%&^&*)">Pretty checkbox 4</label>
<input class="pretty" id="!@##$%^%&^&*)" type="checkbox">

```
now work.