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`