Merge pull request #308 from riking/patch-3

Add pull-update instructions to README

README.md

@@ -11,6 +11,10 @@ Clone MCEdit:
 ```bash
 git clone --recursive https://github.com/mcedit/mcedit
 ```
+Or, if you've already cloned MCEdit in the past and need to update, go to the existing source folder:
+```bash
+git pull --recurse-submodules
+```
 
 Optionally (but highly recommended), setup and activate [virtualenv](http://pypi.python.org/pypi/virtualenv). virtualenv will simplify development by creating an isolated and barebones Python environment. Anything you install while virtualenv is active won't affect your system-wide Python installation, for example.