* Replaced all from ...py23 import * with explicit name imports, or removed completely when possible.
* Replaced tounicode() with tostr()
* Changed all BytesIO ans StringIO imports to from io import ..., replaced all UnicodeIO with StringIO.
* Replaced all unichr() with chr()
* Misc minor tweaks and fixes
we could alternatively decode these version fields as a long integer like we do elsewhere
for similar table versions, but I am not sure whether external code relies on them being
like they are now (i.e. compact decimal float).
https://github.com/fonttools/fonttools/issues/944
otherwise one gets AttributeError: 'module' object has no attribute 'block'
I noticed this by change. The whole SIL lz4-compressed Glif/Silf tables is still untested...
