install_notes

* Put raspbian stretch lite on a 8gb card
* On sd card, set wlan in /etc/wpa_supplicant/wpa_supplicant.conf:
  network={
      ssid="IFK"
      psk="my password here"
      key_mgmt=WPA-PSK
  }
* On sd card, activated ssh:
  touch <boot partition>/ssh
* Started installing opencv by these instructions for raspbian jessie:
  https://www.pyimagesearch.com/2015/12/14/installing-opencv-on-your-raspberry-pi-zero/
  skipped gtk stuff, opencv_contrib, also skipped virtualenv - but installed pip
  used this cmake:
  cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D CXX=g++ ..
  ...that didn't work, math.h not found. think there's something off with gcc here, using g++:
  cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -D CMAKE_CXX_COMPILER=g++ -D CMAKE_C_COMPILER=gcc ..
  ...that didn't work either. tried adding this flag from a bug report:
  cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -DENABLE_PRECOMPILED_HEADERS=OFF ..
  ...that didn't work either, bad variable names in cap_ffmpeg_impl.hpp
  cmake -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local -DENABLE_PRECOMPILED_HEADERS=OFF -DWITH_FFMPEG=OFF ..
  ...worked!
* sudo pip install scipy crashed somehow (no ssh connection next morning). trying:
  sudo pip install scipy --no-cache-dir
  ... crashed again. Increased cache size to 4gb (edit /etc/dphys-swapfile and restart /etc/init.d/dphys-swapfile). Tried again.
  ... worked!