Update README;

README.md

@@ -6,11 +6,6 @@ bits.  The stream will automatically pack this data into compressed bytes, which
 greatly reduced network bandwidth.  This is useful in networking applications where it is necessary
 to reduce network traffic, such as realtime multiplayer games.
 
-How it works
----
-
-Coming soon.
-
 Usage
 ---
 
@@ -32,7 +27,88 @@ stream:read('float') -- 1.8
 Signatures
 ---
 
-Coming soon.
+A signature describes a high level template for a message.  It can be used to reduce duplication in
+reading and writing of messages, and allows reading and writing of tables of data without having to
+write each individual field in a specific order.  First, define a signature:
+
+```lua
+local signature = {
+  { 'playerId', '4bits' },
+  { 'x', '8bits' },
+  { 'y', '8bits' },
+  { 'direction', '9bits' } -- direction in degrees
+}
+```
+
+Then, pack a message into a trickle stream using the signature:
+
+```lua
+local playerData = {
+  playerId = 1,
+  x = 63,
+  y = 41
+  direction = 270
+}
+
+stream:pack(playerData, signature)
+```
+
+`unpack` may be used to decode the stream:
+
+```lua
+local playerData = stream:unpack(signature)
+```
+
+Let's say we only want to send the position of the player if it has changed.  Right now this isn't
+possible with our signature, because we have to send 8 bits for the x position and 8 bits for the y
+position to keep the structure of the signature uniform for the receiving end.  **Delta groups**
+provide a mechanism to specify these optional groups of data.
+
+To declare a delta group, specify a `delta` key in the signature table:
+
+```lua
+local signature = {
+  { 'playerId', '4bits'},
+  { 'x', '8bits' },
+  { 'y', '8bits' },
+  { 'direction', '9bits' },
+  delta = {
+    { 'x', 'y' },
+    'direction'
+  }
+}
+```
+
+What we've done is defined two optional pieces of our message: a group for the position of the
+player and a group for the direction of the player.  Now, if we pack a message like this:
+
+```lua
+local playerData = {
+  playerId = 1,
+  x = nil,
+  y = nil,
+  direction = nil
+}
+
+stream:pack(playerData, signature)
+```
+
+trickle will only pack the 4 bit player id into the message, which saves 25 bits!  Internally,
+a single bit is added to the beginning of the message for each delta group, signifying whether or
+not its data is present.  This means that if a delta group contains more than one key (such as the
+'x' and 'y' group above), either all of the data must be present or all of it must be `nil`.  This,
+for example, would result in an error:
+
+```lua
+local playerData = {
+  playerId = 1,
+  x = 17,
+  y = nil,
+  direction = 90
+}
+
+stream:pack(playerData, signature) -- Error: Only part of message delta group "x, y" was provided.
+```
 
 Documentation
 ---