Fix CMake issue with PGI and README update (#136)

* Remove -Wall for PGI compiler
* Update README

Author: st4rl3ss

CMake/config/CompilerFlagsHelpers.cmake

@@ -123,7 +123,7 @@ foreach(COMPILER_LANGUAGE ${SUPPORTED_COMPILER_LANGUAGE_LIST})
 
 	## rest of the world
 	else()
-		set(CMAKE_${COMPILER_LANGUAGE}_WARNING_ALL "")
+		set(CMAKE_${COMPILER_LANGUAGE}_WARNING_ALL "-Wall")
 		set(CMAKE_${COMPILER_LANGUAGE}_DEBUGINFO_FLAGS "-g")
 
 		set(CMAKE_${COMPILER_LANGUAGE}_OPT_NONE "-O0")
@@ -141,6 +141,9 @@ foreach(COMPILER_LANGUAGE ${SUPPORTED_COMPILER_LANGUAGE_LIST})
 			## Intel O3 is extreme
 			set(CMAKE_${COMPILER_LANGUAGE}_OPT_AGGRESSIVE "-O2")
 		endif()
+		if (CMAKE_${COMPILER_LANGUAGE}_COMPILER_ID STREQUAL "PGI")
+			set(CMAKE_${COMPILER_LANGUAGE}_WARNING_ALL "")
+		endif()
 	endif()
 
 endforeach()