Add mp3 volume function
"setiOSAudioStreamVolume"
Merge pull request #3 from pchan126/feature/mp3Volume

Add mp3 volume function (reverse-merged from commit 228725ac9d0c07623f74c137978e804f11ab5d2f)
- Removed the solution folder from the VS2010 build.
- Reversed the merge pull request #3 from pchan126/feature/mp3Volume accidentally added to Master.

"Add mp3 volume function (reverse-merged from commit 228725ac9d0c07623f74c137978e804f11ab5d2f)"
- Added VS2012 support.
- Updated GoogleTest to support VS2012.