add simple usage

README.rst

@@ -5,11 +5,11 @@ PyInvoice
 .. image:: https://api.travis-ci.org/CiCiApp/PyInvoice.svg?branch=master
     :target: https://github.com/CiCiApp/PyInvoice
 
-Invoice/receipt generator.
+Invoice/Receipt Generator.
 
 Dependency
 ----------
-* reportlab
+* Reportlab
 * Python 2.6+/3.3+
 
 +-------------------+-------------------+-------------------+-------------------+-------------------+
@@ -26,6 +26,61 @@ Dependency
 | Reportlab 3.2     |                   | ✓                 | ✓                 | ✓                 |
 +-------------------+-------------------+-------------------+-------------------+-------------------+
 
+Install
+-------
+
+.. code-block:: bash
+
+    pip install pyinvoice
+
+Usage
+-----
+
+.. code-block:: python
+
+    from datetime import datetime, date
+    from pyinvoice.models import InvoiceInfo, ServiceProviderInfo, ClientInfo, Item, Transaction
+    from pyinvoice.templates import SimpleInvoice
+    
+    doc = SimpleInvoice('invoice.pdf')
+    
+    # Paid stamp, optional
+    doc.is_paid = True
+    
+    doc.invoice_info = InvoiceInfo(1023, datetime.now(), datetime.now())  # Invoice info, optional
+    
+    # Service Provider Info, optional
+    doc.service_provider_info = ServiceProviderInfo(
+        name='PyInvoice',
+        street='My Street',
+        city='My City',
+        state='My State',
+        country='My Country',
+        post_code='222222',
+        vat_tax_number='Vat/Tax number'
+    )
+    
+    # Client info, optional
+    doc.client_info = ClientInfo(email='client@example.com')
+    
+    # Add Item
+    doc.add_item(Item('Item', 'Item desc', 1, '1.1'))
+    doc.add_item(Item('Item', 'Item desc', 2, '2.2'))
+    doc.add_item(Item('Item', 'Item desc', 3, '3.3'))
+    
+    # Tax rate
+    doc.set_item_tax_rate(20)  # 20%
+    
+    # Transactions detail, optional
+    doc.add_transaction(Transaction('Paypal', 111, datetime.now(), 1))
+    doc.add_transaction(Transaction('Strip', 222, date.today(), 2))
+    
+    # Optional
+    doc.set_bottom_tip("Email: example@example.com<br />Don't hesitate to contact us for any questions.")
+    
+    doc.finish()
+
+
 License
 -------
 MIT