install requirements on startup in dev mode

Author: nvdk

start.sh

@@ -1,6 +1,7 @@
 #! /usr/bin/env bash
 set -eu
 if [ ${MODE:-""} == "development" ]; then 
+    if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     exec python web.py
 else 
     exec gunicorn -k egg:meinheld#gunicorn_worker -c "$GUNICORN_CONF" "$APP_MODULE"