tell anyone that might want to ignore their editor choice's backup files that there is a better way - thanks @pnasrat

.gitignore

@@ -1,3 +1,6 @@
+# Docker project generated files to ignore
+#  if you want to ignore files created by your editor/tools,
+#  please consider a global .gitignore https://help.github.com/articles/ignoring-files
 .vagrant*
 bin
 docker/docker