Update to cmake 3.1

CMakeLists.txt

@@ -1,5 +1,7 @@
-cmake_minimum_required(VERSION 3.0 FATAL_ERROR)
-cmake_policy(SET CMP0054 NEW)
+cmake_minimum_required(VERSION 3.1 FATAL_ERROR)
+
+# TODO Remove this deprecated policy switch once we're on cmake 3.4 or later
+cmake_policy(SET CMP0065 OLD)
 
 # TODO Perf test:
 #  - try if setting CRYPTOPP_NATIVE_ARCH=ON and adding -march=native to the compile commands for cryfs source files makes a difference

README.md

@@ -44,7 +44,7 @@ Requirements
 ------------
   - Git (for getting the source code)
   - GCC version >= 5.0 or Clang >= 4.0
-  - CMake version >= 3.0 
+  - CMake version >= 3.1
   - libcurl4 (including development headers)
   - Boost libraries version >= 1.65.1 (including development headers)
     - filesystem