Merge pull request #5 from swift-nav/ababu/update_min_cmake_version

Update CMake minimum required version to 3.13

Author: adharsh

CMakeLists.txt

@@ -70,7 +70,7 @@
 ## - GFLAGS_INSTALL_SHARED_LIBS
 ## - GFLAGS_INSTALL_STATIC_LIBS
 
-cmake_minimum_required (VERSION 3.0.2 FATAL_ERROR)
+cmake_minimum_required (VERSION 3.13 FATAL_ERROR)
 
 if (POLICY CMP0042)
   cmake_policy (SET CMP0042 NEW)