Mapbuffer

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* test: adds github action
* perf: make robust to network access patterns by caching header
* fix: f was not defined
* refactor: remove unused ffs implementation

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* chore: build py39 with appveyor on windows

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* chore: fix appveyor artifact collection

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* chore: update changelog
* feat: support for mmapped files
* fix: try to make this compile under windows
* chore: update build system
* compile: dont bother with 32 bit windows
* fix: windows uses cl for compilation
* fix: no python dir in this appveyor deployment

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* chore: update unit in perf tests from sec to msec
* test: ensure "not in" is tested as well as "in"
* chore: add .DS\_Store to gitignore
* chore: add changelog authors
* chore: add requirements\_dev.txt
* chore: add appveyor
* chore: introduce tox, drop py27
* chore: add build system
* test: check for missing keys
* fix: ensure missing keys return -1
* docs: update perf chart for c-ext
* perf: use C ext to improve index lookup
* test: ensure that empty buffer key access errors
* feat: add \_\_contains\_\_ and get
* docs: add version badge

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* fix: explainatory text was in the wrong place
* docs: add benchmark pic
* chore: added benchmarks
* perf: slightly faster mapbuf construction
* docs: discuss design
* docs: link to flexbuffers
* docs: versus flexbuffers
* docs: add installation instructions