Merge pull request #48 from stitchEm/w-m/macports-ffmpeg

MacPorts: ensure ffmpeg is installed w/ rtmpdump & non-free codecs

doc/BUILD.md

@@ -14,7 +14,8 @@ sudo port install CMake bison doxygen yasm ninja ccache
 
 # Libraries
 sudo port install opencv glew gsed jpeg libpng \
-          tiff faac faad2 ceres-solver glfw ffmpeg glm OpenEXR
+          tiff faac faad2 ceres-solver glfw glm OpenEXR \
+          ffmpeg +gpl2 +librtmp +nonfree
 ```
 
 ```