This adds support for Unicode 8.0.0 on Python 3.5, 9.0.0 on 3.6, and 10.0.0 on 3.7-dev.
* `allkeys.txt` are shipped for 8.0.0, 9.0.0, and 10.0.0 as well as the exisiting 5.2.0 and 6.3.0
* support for `implicitweights` in collation element tables was added
* the implicit weight calculation code was extended not only to support `implictweights` but also code point additions to the blocks in the Han Database
* `from pyuca import Collator` will give a Collator appropriate to the Python version (not just 2 vs 3 but 3.4 vs 3.5 vs 3.6 vs 3.7+)
* fixed some inconsistent code formatting and misspellings