Redefinable options for parser

[shuhrat]

Could you please add re definable options from API for HTML parser
now they are strongly defined, and there is now way to change them
https://github.com/bem/html-differ/blob/master/lib/html-differ.js#L19

[mishanga]

This is needed for http://nda.ya.ru/3QTQNa

[eGavr]

I don't mind ^_^

/cc @tadatuta

[tadatuta]

sure, let's add it.

@mishanga I'm sure you are aware of https://github.com/andrewblond/enb-bem-tmpl-specs
Do you really need another tool for SERP?

[shuhrat]

@tadatuta I already fixed(refactored) and pulled a request, #49