Remove 'for' argument from tag

Hi,

I've just started using **django-fluent-comments**. I'm a big fan as the Ajax approach allows me to leave my views alone :) And it works really well.

I ended up using the latest on `master` and I came across this problem running Django 1.6.8 and Python 2.6. It seems that the custom tag doesn't really handle the use of `for` in the tag usage as it tries to resolve `for` as a context variable instead of leaving it as syntax.

I've opted for a fairly dull fix here. I guess ideally we'd write a tag that properly supported the syntax but I'm not experienced with writing such tags with the Django API and I doubt you want to depend on something like django-classy-tags.

As a separate note, I've also ended up removing a lot of the 'fadeIn' stuff from the Javascript as I am not partial to the look. I've just commented it out for the moment but if you'd like a pull request which makes it optional then I could try my hand at that.

Thanks again, it is a great project which has been super easy to use,
Michael