Update readme and update min requirement for ROOT

CMakeLists.txt

@@ -50,7 +50,7 @@ dd4hep_configure_output( OUTPUT "${PROJECT_BINARY_DIR}" INSTALL "${CMAKE_INSTALL
 #
 # Include ROOT
 #
-find_package ( ROOT REQUIRED COMPONENTS Geom GenVector Eve Gui Graf3d RGL EG)
+find_package ( ROOT 6.08 REQUIRED COMPONENTS Geom GenVector Eve Gui Graf3d RGL EG)
 include(${ROOT_USE_FILE})
 message ( STATUS "ROOT_VERSION: ${ROOT_VERSION}" )
 #

README.md

@@ -39,7 +39,7 @@ system before building and running the examples
 
 - **Mandatory**
 
-  CMake (version 2.8 or higher), ROOT (version 5.30 or higher) and Boost installations are mandatory.
+  CMake (version 3.3 or higher), ROOT (version 6.08 or higher) and Boost (version 1.49 or higher) installations are mandatory.
 
 - **Optional**