Allow personal customizations via ~/.laptop.local

Use same `.local` convention as https://github.com/thoughtbot/dotfiles.

Manifest.linux

@@ -15,3 +15,4 @@ common-components/default-gems
 linux-components/heroku
 linux-components/github
 linux-components/rcm
+common-components/personal-additions

Manifest.mac

@@ -16,3 +16,4 @@ common-components/default-gems
 mac-components/heroku
 mac-components/github
 mac-components/rcm
+common-components/personal-additions

README.md

@@ -71,6 +71,21 @@ What it sets up
 
 It should take less than 15 minutes to install (depends on your machine).
 
+Make your own customizations
+----------------------------
+
+Put your customizations in `~/.laptop.local`. For example, your
+`~/.laptop.local` might look like this:
+
+    #!/bin/sh
+
+    brew tap phinze/homebrew-cask
+    brew install brew-cask
+
+    brew cask install dropbox
+    brew cask install google-chrome
+    brew cask install rdio
+
 Credits
 -------
 

common-components/personal-additions

@@ -0,0 +1,2 @@
+fancy_echo "Installing your personal additions from ~/.laptop.local ..."
+  [[ -f ~/.laptop.local ]] && source ~/.laptop.local

linux

@@ -176,3 +176,7 @@ fancy_echo "Installing rcm, to manage your dotfiles ..."
   rm -f /tmp/rcm_1.1.0_all.deb
 ### end linux-components/rcm
 
+fancy_echo "Installing your personal additions from ~/.laptop.local ..."
+  [[ -f ~/.laptop.local ]] && source ~/.laptop.local
+### end common-components/personal-additions
+

mac

@@ -166,3 +166,7 @@ fancy_echo "Installing rcm, to manage your dotfiles ..."
   brew install rcm
 ### end mac-components/rcm
 
+fancy_echo "Installing your personal additions from ~/.laptop.local ..."
+  [[ -f ~/.laptop.local ]] && source ~/.laptop.local
+### end common-components/personal-additions
+