Reduce binary size to ~1MB

- Recompiled main.cpp with -s WASM=1
- Recompiled FFTW with O3 flag

compile.sh

@@ -2,7 +2,7 @@
 
 echo "static const char * BUILD_TIMESTAMP=\"`date`\";" > build_timestamp.h
 
-em++ -Wall -Wextra -O3 -std=c++11 -s USE_SDL=2 ./main.cpp -o wave.js -I ./fftw-3.3.3/api ./lib/libfftw3f.a \
+em++ -Wall -Wextra -O3 -std=c++11 -s USE_SDL=2 -s WASM=1 ./main.cpp -o wave.js -I ./fftw-3.3.3/api ./lib/libfftw3f.a \
     -s EXPORTED_FUNCTIONS='["_getText", "_getSampleRate", "_setText", "_getAverageRxTime_ms", "_setParameters",
                             "_getFramesLeftToRecord", "_getFramesToRecord",
                             "_getFramesLeftToAnalyze", "_getFramesToAnalyze",