update README; make main.py executable

README.md

@@ -1,3 +1,12 @@
 # marginbot
 
-Cryptocurrency micro trading bot
+Cryptocurrency micro trading bot
+
+```
+cd marginbot/
+cp config.json.example config.json
+python -m venv .venv
+source .venv/bin/activate
+pip install -r requirements.txt
+./main.py
+```