Update readme, use a sort order for install scripts

README.md

@@ -1,6 +1,12 @@
-### script run plan
-- run `./pre_install_*` scripts
-- run `./install_programs` to install/build/etc programs
-- run `./copy_configs` to copy configs/scripts/executables into place
-- run `./post_config_*` scripts
+# repo containing configs and scripts to set up a box
+
+### prerequisites
+- install git if not already installed
+- clone this repo
+- if on macOS, install [homebrew](https://brew.sh/)
+- export the env var `BOX_SETUP_OS` to indicate the operating system
+    - (options defined in `set_env_vars` file)
+
+### script run
+- from the repo's root directory, run `./setup_this_box`