DOC: Updating Documentation

Raised Visual Studio requirement to 15

README.md

@@ -17,7 +17,7 @@ SuperBuild CMake Project.
 * C++ Compiler
  * XCode 7.1 or greater - **Note if using XCode 8.x you will need the 10.11 SDK (there is an issue with QuickTime and OpenCV)**
  * GCC 4.8 or higher
- * Visual Studio 2013 64 bit
+ * Visual Studio 2015 64 bit
 * Ubuntu 16.04 specific
  * sudo apt-get install m4
  * sudo apt-get install build-essential