README.md in cose-0.3.0 vs README.md in cose-0.4.0

@@ -23,16 +23,35 @@
 
 ## Usage
 
 ### Key Objects
 
+```ruby
+cbor_data = "..."
+
+key = COSE::Key.deserialize(cbor_data)
+
+case key.class
+when COSE::Key::EC2
+  key.curve
+  key.x_coordinate
+  key.y_coordinate
+  key.d_coordinate
+when COSE::Key::RSA
+  key.modulus_n
+  key.public_exponent_e
+when COSE::Key::Symmetric
+  key.key_value
+end
+```
+
 #### EC2
 
 ```ruby
 cbor_data = "..."
 
-key = COSE::Key::EC2.from_cbor(cbor_data)
+key = COSE::Key::EC2.deserialize(cbor_data)
 
 key.curve
 key.x_coordinate
 key.y_coordinate
 key.d_coordinate
@@ -41,12 +60,23 @@
 #### Symmetric
 
 ```ruby
 cbor_data = "..."
 
-key = COSE::Key::Symmetric.from_cbor(cbor_data)
+key = COSE::Key::Symmetric.deserialize(cbor_data)
 
 key.key_value
+```
+
+#### RSA
+
+```ruby
+cbor_data = "..."
+
+key = COSE::Key::RSA.deserialize(cbor_data)
+
+key.modulus_n
+key.public_exponent_e
 ```
 
 ### Signing Objects
 
 #### COSE_Sign