Add position-related features.

Change __version__ to '0.4'. Update README.md. Update example.py.

README.md

@@ -2,18 +2,17 @@
 
 This is a library-like application, which operates with orders and positions on your account.
 
-*Current version:* **0.3**
+*Current version:* **0.4**
 #### Features:
 * Creating an cancelling orders on your account. Stop-loss, Limit, passive, reduce-only, close-only, hidden orders supported.
 * Preventing these orders for being lost, cancelled or rejected: Supervisor will place them anew.
 * Supervisor closes all orders, which are not supervised.
 * When the supervised order has been filled, Supervisor will not try to place it. 
 * Put callbacks on supervised orders, which are called when order has been filled, partially executed or cancelled.
+* Set and maintain the position size.
 #### In develop:
-* Manage positions on your account.
-    * Maintaining position size.
-    * Various market-price or limit entries in position.
-    * Enter position with rebate by tracking last market price and moving limit order up.
+* Various market-price or limit entries in position.
+* Enter position with rebate by tracking last market price and moving limit order up.
 
 ## Getting Started
 
@@ -112,6 +111,12 @@ from supervisor import Supervisor
 supervisor = Supervisor(interface=exchange)
 ```
 
+Set necessary position size, Supervisor will fix it:
+
+```python
+supervisor.position = 150
+```
+
 Create order:
 
 ```python

example.py

@@ -8,14 +8,20 @@
 TEST_API_SECRET = 'your-api-secret'
 
 if __name__ == '__main__':
+    # Exchange is a interface-like class to call api methods
     exchange = Exchange(api_key=TEST_API_KEY, api_secret=TEST_API_SECRET,
                         test=True, symbol='XBTUSD')
     supervisor = Supervisor(interface=exchange)
 
+    # create Order objects
     stop_loss = Order(order_type='Stop', stop_px=Decimal(2000), qty=10, side='Sell')
     tp1 = Order(order_type='Limit', price=Decimal(15000), qty=6, side='Sell', passive=True, reduce_only=True)
     tp2 = Order(order_type='Limit', price=Decimal(20000), qty=4, side='Sell', hidden=True)
 
+    # set needed position price
+    supervisor.position_size = 10
+
+    # attach some callbacks to stop-loss, note that events starts with "_"
     stop_loss._on_reject = lambda: print('Rejected')
     stop_loss._on_fill = lambda: print('We lost position(')
     stop_loss._on_cancel = lambda: print('Trading without stops is risking ;)')

supervisor/__init__.py

@@ -1,3 +1,3 @@
 from supervisor._supervisor import *
 
-__version__ = '0.3'
+__version__ = '0.4'