Add test files to NAudioTests and remove absolute paths

Test files should be added to NAudioTests project. For example

var testFile = @"C:\Users\Mark\Code\CodePlex\pcm mono 16 bit 8kHz.wav";

from GsmEncodeTest.cs. Some tests failed or ignored due to absense of these files.

@markheath, can you attach here the following files:

C:\Users\Mark\Code\CodePlex\gsm.wav
F:\Recording\wav\pcm\16bit mono 8kHz.wav
F:\Recording\wav\pcm\32bit stereo 8kHz.wav
C:\Users\Public\Music\Coldplay\X&Y\01-Square One.mp3
D:\Audio\Music\Coldplay\Mylo Xyloto\03 - Paradise.mp3
C:\Users\mheath\Downloads\NAudio\AAC\halfspeed.aac
C:\Users\Mark\Downloads\Region-1.wav

and mp3 files from C:\Users\Mark\Downloads\NAudio. I or somebody else will add them to tests project.

[markheath]

maybe, will try to review those tests at some point to see what audio files are actually needed. My main focus for now is getting ready for 1.8 release

[KvanTTT]

Maybe it’s time to try GitHub large file storage 😎