Update .gitignore and add doc-mode.el.

.emacs.d/snippets/c++-mode/sptr

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: shared_ptr
+# key: sptr
+# --
+std::shared_ptr<${1:type}> ${2:name}$0

.emacs.d/snippets/c++-mode/todo

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: todo_full
+# key: todo
+# --
+`(yas-with-comment "TODO: ")`

.emacs.d/snippets/c++-mode/uptr

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: unique_ptr
+# key: uptr
+# --
+std::unique_ptr<${1:type}> ${2:name}$0

.emacs.d/snippets/c++-mode/wptr

@@ -0,0 +1,5 @@
+# -*- mode: snippet -*-
+# name: weak_ptr
+# key: wptr
+# --
+std::weak_ptr<${1:type}> ${2:name}$0