Python3 compatibility, fulltext tag search and document update

[dany-nonstop]

Changes made

• added compatibility with python3, change all use of django.utils.six (deprecated) to six
• added tag option autocomplete_fulltext to make full text search on autocompletion, default is off
• updated document on default setting, especially when jQuery is loaded in the other part of the project
• updated document on autocomplete_fulltext
• fix "division by 0" when calling weight() on a list of new tags imported without any count (everything is 0)

they may break tagulous on python2, never tested.

[dany-nonstop]

@radiac I like the concise tag tree implementation in tagulous and have used it in my python3 + django3 project. While working on my project I have added these changes to make it work. Thanks for making it available to the community.

[coveralls]

Coverage increased (+0.003%) to 95.203% when pulling 9efab26 on dany-nonstop:develop into b73b6c9 on radiac:develop.

[dany-nonstop]

@radiac whenever you're available, could you please check the code and merge them to your current branch? thanks.

[dany-nonstop]

Hi, @radiac how can I contribute my code to your project? Thanks!

[BoPeng]

I was looking for a similar features but I simply used a customized autocomplete_view function. Perhaps this is why @radiac did not want to add this as one of the core features?

[dany-nonstop]

Hi, @BoPeng your comment is highly appreciated, thanks, I would say it's a possible solution. But I don't know why @radiac didn't even care to comment before closing this PR.

[BoPeng]

I have a PR pending for more flexible view function. It is much simpler than your solution but might still not be merged. I am using a fork for my project anyway.

[radiac]

Sorry for the delay - I haven't closed the pr, it looks interesting, but unfortunately it came in while I was finishing up the refactor to remove py2, so it wasn't a simple one to merge - I'll need to cherry pick bits. The past few months have been very busy, but I hope to get to it soon.

[radiac]

Thanks for the PR, finally had a chance to pick out the compatible changes and add some tests. Closing, merged via #128.