Unit test

[jean-barre]

I do not know if this is fixed by the XCode environment but I had issues running the FileWritingTests on Linux:

• the filepath of created files is not relative
  I had to edit lines 39 and 44 to return audioFile.save ("./audio-write-tests/...
• the repertory audio-write-tests does not exist.
  I had to create it.

Again this may be due to the environment. Great work

[adamstark]

Thanks! I've now fixed this on the develop branch