reproduce #48
Recover `zlib.h` files from numenta:master@46835bfdf53b4b2d12f88ed1fd0dd02f33bf22aa
Remove reproduction of #48 after fixed it
Merge branch 'master' of https://github.com/numenta/nupic.core into 48-zlib
Merge pull request #97 from utensil/48-zlib

Recover `zlib.h` in `external`
Remove custom stylesheet, fall back to default because qmi isn't compatible with Doxygen 1.8.7
Merge branch 'master' of https://github.com/numenta/nupic.core into 80-engine-api-doc
Merge pull request #100 from utensil/80-engine-api-doc

Remove custom stylesheet, fall back to default because qmi isn't compatible with Doxygen 1.8.7