add cpplint and add hotkey for switch-header-source on OSX

docs/atom.md

 # Atom
 
 [TOC]
 
 ## Workflow
 
 A typical Atom workflow consists of the following.
 
 1. Use `Ctrl-Shift-R` to find a symbol in the `.tags` file or `Ctrl-P` to find
    a file by name.
-2. Switch between the header and the source using `Alt-O`.
+2. Switch between the header and the source using `Alt-O`(`Ctrl-Opt-S` on OSX).
 3. While editing, `you-complete-me` package helps with C++ auto-completion and
    shows compile errors through `lint` package.
 4. Press `Ctrl-Shift-P` and type `format<Enter>` to format the code.
 5. Select the target to build by pressing `F7` and typing, for example,
    `base_unittests`.
 6. Rebuild again by pressing `F9`.
 
 ## Atom packages
 
 To setup this workflow, install Atom packages for Chrome development.
 
 ```
 $ apm install build-ninja clang-format \
-    linter linter-eslint switch-header-source you-complete-me
+    linter linter-cpplint linter-eslint switch-header-source you-complete-me
 ```
 
 ## Autocomplete
 
 Install C++ auto-completion engine.
 
 ```
 $ git clone https://github.com/Valloric/ycmd.git ~/.ycmd
 $ cd ~/.ycmd
 $ ./build.py --clang-completer
@@ skipping 85 matching lines @@
 on a project that frequently uses `foo` or `bar` in files names, you can create
 a small `.tags` file to efficiently search the symbols within these files. Be
 sure to use "Exuberant Ctags."
 
 ```
 $ git ls | egrep -i "foo|bar" | ctags -f .tags -L -
 ```
 
 Don't create a ctags file for the full Chrome repository, as that would result
 in ~9GB tag file that will not be usable in Atom.