Restructured CMake file to include headers, and to be better organized

src/CMakeLists.txt

@@ -1,9 +0,0 @@
-set(FILES alias.cpp content.cpp iterator.cpp node.cpp parserstate.cpp
-          scalar.cpp scanscalar.cpp sequence.cpp stream.cpp
-          exp.cpp map.cpp parser.cpp regex.cpp scanner.cpp
-          scantoken.cpp simplekey.cpp
-		  emitter.cpp emitterstate.h emitterstate.cpp emitterutils.h emitterutils.cpp
-		  ostream.cpp)
-
-include_directories(${YAML_CPP_SOURCE_DIR}/include)
-add_library(yaml-cpp ${FILES})