Update README.md

Additional instructions about cmake.

Author: hani-girgis

README.md

@@ -24,14 +24,16 @@ Please cite the following paper:
 Requirments:
 
 	GNU g++ 7.5.0 or later
-	You may change the compiler in the CMakeLists.txt: set(CMAKE_CXX_COMPILER g++-7)
 
 To Compile:
 
-	mkdir bin
-	cd bin
-	cmake ..
-	make
+	> mkdir bin
+	> cd bin
+	(if your default compiler meets the version requiremet) 
+	> cmake ..
+	(if you would like to specify a different compiler that meets the requirement)
+ 	> cmake .. -DCMAKE_CXX_COMPILER=your_compiler_name_for_example_g++-7
+	> make
 
 To Test: