rename initialize() to begin(), Arduino's naming convention

analyze_guitartuner.cpp

  *  @param threshold Allowed uncertainty
  *  @param cpu_max   How much cpu usage before throttling
  */
-void AudioAnalyzeGuitarTuner::initialize( float threshold ) {
+void AudioAnalyzeGuitarTuner::begin( float threshold ) {
     __disable_irq( );
     process_buffer = false;
     yin_threshold  = threshold;

analyze_guitartuner.h

      *
      *  @return none
      */
-    void initialize( float threshold );
+    void begin( float threshold );
     
     /**
      *  sets threshold value

examples/Analysis/GuitarTuneNotes/GuitarTuneNotes.ino

      *  Initialize the yin algorithm's absolute
      *  threshold, this is good number.
      */
-    tuner.initialize(.15);
+    tuner.begin(.15);
     pinMode(LED_BUILTIN, OUTPUT);
     playNoteTimer.begin(playNote, 1000);
 }