* 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
Today, Apple has kindly fixed a bug in the [specification of the
meta table](https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6meta.html). The existing fonttools implementation matches the
revised specification. Therefore, the comments about fonttools
intentionally deviating from Apple's spec can be removed.
Because I could not find any fonts with “dlng” (design languages) or
“slng” (supported languages) sub-tables, these are not implemented yet.
We could easily implement them according to spec, but it is unclear
to what extent the spec is matching reality.
