Update latexmk install instructions

README.md

@@ -42,7 +42,14 @@ ShareLaTeX should run on OS X and Linux. You need:
 * [Node.js](http://nodejs.org/) 0.10 or greater
 * The [grunt](http://gruntjs.com/) command line tools (Run `npm install -g grunt-cli` to install them)
 * A local instance of [Redis](http://redis.io/) (version 2.6 or later) and [MongoDB](http://www.mongodb.org/) running on their standard ports.
-* An up to date version of [TeXLive](https://www.tug.org/texlive/), with the `latexmk` program installed (should be included by default in TeXLive).
+* An up to date version of [TeXLive](https://www.tug.org/texlive/), with the `latexmk` program installed. You need latexmk from TeXLive 2013 (or the later). If you're on an older version, or aren't sure, then the following commands will install the latest version locally:
+
+  ```bash
+  $ mkdir ~/bin 
+  $ curl http://mirror.physik-pool.tu-berlin.de/tex-archive/support/latexmk/latexmk.pl > ~/bin/latexmk
+  $ chmod a+x ~/bin/latexmk
+  $ export PATH=~/bin:$PATH
+  ```
 
 Config
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