Update BUILD.md

Add the supported python version as requested here: #34

BUILD.md

@@ -11,7 +11,7 @@ GPUPerfAPI no longer uses git submodules to reference dependent repositories. In
 order to clone/update any dependent repositories.
 
 #### Prerequisites
-  * Python, which can be installed from https://www.python.org/
+  * Python, which can be installed from https://www.python.org/. Either Python 2.7 or 3.x should work.
   * CMake 3.5.1 or newer
     * For Windows, this can be downloaded from https://cmake.org/download/
     * For Linux, this can be installed using: sudo apt-get install cmake
@@ -31,7 +31,7 @@ order to clone/update any dependent repositories.
 present on the system, this script will instead do a "git pull" on those repositories to ensure that they are up to date. Please re-run
 this script everytime you pull new changes from GPA repository.
  * NOTE: For GPA 3.3 or newer, if you are updating an existing clone of the GPA repo from an earlier GPA release, you will first need to delete the Common/Lib/Ext/GoogleTest directory. Starting with GPA 3.3, GPA is now using a fork of the official GoogleTest repo. Failure to remove this directory will lead to git errors when running PreBuild.py or UpdateCommon.py.
- * This script will also download and execute the Vulkan™ SDK installer.
+ * This script will also download and execute the Vulkan™ SDK installer.
    * On Windows, running the installer may require elevation.  If you've previously installed the required Vulkan version, UpdateCommon will simply copy the files form the default installation location into the correct place into the GPUPerfAPI directory tree.
    * UpdateCommon is set up to install the version of the Vulkan SDK which was used during development. If you want to use a newer version of the SDK, the following file will need to be updated:
      * [UpdateCommonMap.py](Scripts/UpdateCommonMap.py)