Set default encoding in the DOMDocument object

[idimopoulos]

Solves #167 (If I am correct).

[goetas]

Hi, thanks for the PR. Is there a way to test this?

[idimopoulos]

@goetas I am working on it right now. There is a very easy to test this in \Masterminds\HTML5\Tests\Parser\DOMTreeBuilderTest::testDocument by simply checking if the resulting $doc object has the correct (or default) encoding.

What I am worrying about though, is whether the encoding should derive by the document itself i.e. the charset attribute in the head HTML element tag. I will be back shortly with something.

[idimopoulos]

I forced pushed to add a failing test first and then I will push the fix.
The thing is that I am not entirely sure about the nature of the parser.
In \Masterminds\HTML5::parse the scanner is instantiated with the options !empty($options['encoding']) ? $options['encoding'] : 'UTF-8'

However, this means only that the scanner is meant to scan using a 'UTF-8' parser (I mean that it will deal with the document considering that it is a UTF-8 document even if it is not.
However, the DOMTreeBuilder, that actually has the $doc property, should have the encoding of the document/input itself. Since it is an HTML5 parser, I can assume that an HTML is expected to be passed. However, the input is not required to build the DOMTreeBuilder.

I see all over around that the UTF-8 is used as the default option but I am not sure whether that should apply for the DOMTreeBuilder (maybe you people can shed some light here).
In any way, I am providing the fix as in our case, as I mentioned in #167, Symfony uses the new \DOMDocument('1.0', $charset); which is passed in the method to build the Document so even for the legacy cases, the charset is not detected through the head metatag. Thus, at least to be consistent to begin with, we could have this set to UTF-8 by default.

Do you think I need to open an issue to automatically detect the charset from the HTML if available?

[idimopoulos]

Sorry I messed up a bit with the commit messages.

[goetas]

Looks good, thanks!