Parser incorrectly collapses whitespace #80
Description
To reproduce: Run the following
$dom = new Dom();
$dom->load('<pre> Hello world</pre>');
echo $dom;
Result:
=> "<pre> Hello world</pre>"
The resultant HTML has its four spaces collapsed to one. This will break any use cases for whitespace sensitive HTML (such as in <pre> tags), and is just bad practise in general, since the parser is silently modifying the HTML. The whitespaceTextNode should already be enabled by default, but even with it enabled manually this still occurs.