os/mac: mark Mavericks as outdated.

Library/Homebrew/os/mac.rb

@@ -34,7 +34,7 @@ module OS
 
     def outdated_release?
       # TODO: bump version when new OS is released
-      version < "10.9"
+      version < "10.10"
     end
 
     def cat

share/doc/homebrew/Installation.md

@@ -10,7 +10,7 @@ it does it too. And you have to confirm everything it will do before it starts.
 
 ## Requirements
 * An Intel CPU <sup>[1](#1)</sup>
-* OS X 10.9 or higher <sup>[2](#2)</sup>
+* OS X 10.10 or higher <sup>[2](#2)</sup>
 * Command Line Tools for Xcode: `xcode-select --install`,
   https://developer.apple.com/downloads or
   [Xcode](https://itunes.apple.com/us/app/xcode/id497799835) <sup>[3](#3)</sup>
@@ -42,7 +42,7 @@ you can assume you will have trouble if you don’t conform. Also, you can find
 PowerPC and Tiger branches from other users in the fork network. See
 [Interesting Taps & Forks](Interesting-Taps-&-Forks.md).
 
-<a name="2"><sup>2</sup></a> 10.9 or higher is recommended. 10.5 - 10.8 are
+<a name="2"><sup>2</sup></a> 10.10 or higher is recommended. 10.5 - 10.8 are
 supported on a best-effort basis. For 10.4 and 10.5, see
 [Tigerbrew](https://github.com/mistydemeo/tigerbrew).