Add gitattribute to force lf line endings

.gitattributes

@@ -0,0 +1,17 @@
+# text=auto is only correctly supported in git 2.10.0
+#  https://github.com/git/git/blob/master/Documentation/RelNotes/2.10.0.txt#L248
+# * text=auto eol=lf
+*.sh text eol=lf
+*.sql text eol=lf
+*.rb text eol=lf
+*.erb text eol=lf
+*.json text eol=lf
+*.yml text eol=lf
+*.builder text eol=lf
+*.js text eol=lf
+*.jbuilder text eol=lf
+*.svg text eol=lf
+*.css text eol=lf
+*.scss text eol=lf
+*.png binary
+*.gif binary