Installation.md

@@ -3,6 +3,8 @@ To make the installation of ShakeMap as simple as possible, we have tried to kee
 
 We also make use of [conda virtual environments](https://conda.io/docs/user-guide/concepts.html#conda-environments). The purpose of this is to try to achieve a fully self-contained environment and avoid conflicts with other software. We have discovered that there are some problems with this strategy in shells other than bash. The use of the install script and conda virtual environments are not required to run ShakeMap, but manually managing the dependencies is difficult and you should be aware that if you choose to do this then you should expect to encounter significant difficulties. That said, the list of dependencies is given in the `environment.yml` file in the root directory. 
 
+Prior to the installation described below, make sure your system has the utilities **curl** and **git**. If it does not, install them before proceeding.
+
 # Instructions
 If you are already using conda virtual environments, deactivate before proceeding
 ```