Pull request for gslab-econ/admin#143: Improve practice task. (#104)

* gslab-econ/admin#143 clarify not to edit run.py

* #143 link to RA manual in 1st paragraph

README.md

@@ -1,6 +1,6 @@
 # GSLab Template 
 
-The GSLab Template is a minimal working demonstration of the tools and organization used by projects in the GSLab. We use [SCons](http://scons.org/) and a few custom builders to execute scripts and track dependencies in a portable and flexible manner.
+The GSLab Template is a minimal working demonstration of the [tools and organization](https://github.com/gslab-econ/ra-manual/wiki/Getting-Started) used by projects in the GSLab. We use [SCons](http://scons.org/) and a few custom builders to execute scripts and track dependencies in a portable and flexible manner.
 
 ## Prerequisites
 
@@ -182,7 +182,7 @@ That's fine, but you'll need version 2.4.0 or later. Just switch `python run.py`
 
 Be aware that the [formatting of the cache](https://bitbucket.org/scons/scons/src/rel_2.5.1/src/CHANGES.txt?at=2.5.1&fileviewer=file-view-default#CHANGES.txt-60) changed in version 2.5.0 of SCons. A cache can get messy and fall out of sync if collaborators use a mix of older and newer versions. 
 
-The version of SCons packaged with this repository is scons-local-3.0.1. Our `run.py` scripts are just wrappers around the `scons.py` included in scons-local.
+The version of SCons packaged with this repository is scons-local-3.0.1. Our `run.py` scripts are just wrappers around the `scons.py` included in scons-local. These files exist only to execute SCons, and you shouldn't need to edit them frequently, if at all. The structure of your SCons tree should be entirely specified in your SConstruct and SConscript files.
 
 #### Where should I track the prerequisites for my repository?