Add AudioMerger class
Add method stub merge(File, File)
Implement merge() operation for two WAV files
Add AudioMerge activity (stub) to test AudioMerger
Add AudioRecorder as service in manifest
Add AudioRecorder and AudioRecordThread
Start AudioRecorder in AudioMergeActivity
Return boolean for whether merge() succeeded
Allow next file path to be set in AudioRecordThread
Add android:exported="true" so activity can be run as main activity
Messing with file paths to make saving start working
Only add portion of second WAV file that comes after the WAV header
Save second file in AudioMergeActivity
Move audio merging into Utils
Change file names and length in test
Use Utils.LoadFile(File) and remove re-implemented readAllBytes(File)
Change AudioMerger.merge() signature to take a List<File>, and update usage in AudioMergeActivity
Implement multi-file WAV merging
Call Utils.AudioMerger.merge, fix an off-by-one error and an increment direction problem
Merge files with lower memory overhead.

Done by buffering from FileInputStream directly to FileOutput stream, rather than
reading into one large array for the whole file and then writing that array.