Bump required CMake version to 3.1.0.

Earlier versions did not include CXX_STANDARD that we use to figure out
what compiler flags needs to be used.

CMakeLists.txt

@@ -1,5 +1,5 @@
 project(PlexMediaPlayer CXX C)
-cmake_minimum_required(VERSION 3.0.0 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.1.0 FATAL_ERROR)
 
 cmake_policy(SET CMP0020 NEW)
 if (POLICY CMP0058)

README.md

@@ -3,7 +3,7 @@
 You need:
 
 * Qt 5.6 alpha
-* cmake 3.0 or newer
+* cmake 3.1 or newer
 * ninja is recommended for building
 
 Special Qt requirements: