Add tokenquote interface

python/README.md

@@ -638,7 +638,7 @@ Define limits of value amounts of tokens that individual addresses can
 hold.
 
 Limits are inclusive; a limit for 42 means transfer resulting in a token
-balance \_higher\_ than 42 should be rejected.
+balance *higher* than 42 should be rejected.
 
 A return value of 0 indicates that the token is categorically not
 accepted by the holder.
@@ -650,6 +650,9 @@ accepted by the holder.
 #### Solidity interface definition
 
     interface ITokenLimit {
+        // Returns limit of total value a holder will accept of a specific token.
+        // The value limit returned is inclusive; A limit of 42 means any operation resulting in a balance OVER 42 should be rejected.
+        // A value of 0 means that no value of the token is accepted.
         function limitOf(address _token, address _holder) external view returns(uint256);
     }
 
@@ -657,6 +660,29 @@ accepted by the holder.
 
 - <git://holbrook.no/erc20-limiter.git>
 
+### TokenQuote
+
+Quote an output token value for a given value of input tokens.
+
+Both input and output value is denominated in the smallest available
+unit of respective tokens.
+
+#### ERC165 Interface identifier
+
+dbb21d40
+
+#### Solidity interface definition
+
+    interface ITokenQuote {
+        // Returns, within a current context, what value of outTokens the given value of inTokens translates to.
+        // The values are given in smallest unit of each respective token.
+        function valueFor(address _outToken, address _inToken, uint256 value) external view returns (uint256);
+    }
+
+#### Example implementation
+
+- <git://holbrook.no/erc20-limiter.git>
+
 ### TokenRateChange
 
 Enables detection of properties for CIC tokens that change value over