Changing .gitignore to ignore OS generated files

.gitignore

@@ -4,3 +4,13 @@ personal-9894.md
 # Targets Windows & Unix temporary files
 ~$*
 *~
+
+# OS generated files #
+######################
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db