add .gitattributes file

.gitattributes

@@ -0,0 +1,12 @@
+# Set the deifault behavior, in case people don't have core.autocrlf set.
+* text=auto
+
+# Explicitly declare text files you want to always be normalized and converted
+# to native line endings on checkout.
+*.c   text
+*.cpp text
+*.cxx text
+*.cc  text
+*.h   text
+*.hpp text
+