Update for setup_aimsun.sh (#744)

* Addressing issue #743

This is a fix for Conda having removed support for Python 2.7.4 and not being able to run setup_aimsun.sh

* Uncommented the two lines of code

I've also changed the comment, so people know the purpose of adding the two lines of code.

scripts/setup_aimsun.sh

@@ -1,5 +1,9 @@
 #!/bin/bash
 
+# allows you to access python 2.7.4 which is needed for creating the aimsun_flow environment
+conda config --append channels https://repo.anaconda.com/pkgs/free
+conda config --append channels https://repo.anaconda.com/pkgs/pro
+
 # create the conda environment
 conda create -y -n aimsun_flow python=2.7.4