Add FFmpeg adapter, fix travis and add fields#77

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tmp-hallenser wants to merge 11 commits intoPHPExif:masterfrom

tmp-hallenser:ffmpeg-adapter_fix-travis_add-fields

Commits on Dec 5, 2019

Added option to set path for FFprobe adapter
tmp-hallenser
committed

Commits on Dec 7, 2019

Fixed issue of 3 ISO values
tmp-hallenser
committed