Switch to raw assert for min CMake version

Now that the minimum CMake version is 2.8.11, it seems that CMake now allows
to to assert the minimum CMake version in an included file.

However, you still need to provide a minimum CMake version in the base project
CMakeLists.txt file or CMake provides a warning.

tribits/examples/TribitsExampleProject/CMakeLists.txt

@@ -4,6 +4,10 @@
 #                                                                              #
 ################################################################################
 
+# To be safe, define your minimum CMake version.  This may be newer than the
+# min required by TriBITS.
+CMAKE_MINIMUM_REQUIRED(VERSION 2.8.11 FATAL_ERROR)
+
 # Make CMake set WIN32 with CYGWIN for older CMake versions.  CMake requires
 # this to be in the top-level CMakeLists.txt file and not an include file :-(
 SET(CMAKE_LEGACY_CYGWIN_WIN32 1 CACHE BOOL "" FORCE)

tribits/examples/TribitsHelloWorld/CMakeLists.txt

@@ -1,5 +1,9 @@
 # Example of a simple project that uses TriBITS
 
+# To be safe, define your minimum CMake version.  This may be newer than the
+# min required by TriBITS.
+CMAKE_MINIMUM_REQUIRED(VERSION 2.8.11 FATAL_ERROR)
+
 # Make CMake set WIN32 with CYGWIN for older CMake versions.  CMake requires
 # this to be in the top-level CMakeLists.txt file and not an include file :-(
 SET(CMAKE_LEGACY_CYGWIN_WIN32 1 CACHE BOOL "" FORCE)