Decouple transferable logic from VestedToken

contracts/token/TransferableToken.sol

@@ -0,0 +1,22 @@
+pragma solidity ^0.4.8;
+
+import "./ERC20.sol";
+
+contract TransferableToken is ERC20 {
+  modifier canTransfer(address _sender, uint _value) {
+   if (_value > transferableTokens(_sender, uint64(now))) throw;
+   _;
+  }
+
+  function transfer(address _to, uint _value) canTransfer(msg.sender, _value) returns (bool success) {
+   return super.transfer(_to, _value);
+  }
+
+  function transferFrom(address _from, address _to, uint _value) canTransfer(_from, _value) returns (bool success) {
+   return super.transferFrom(_from, _to, _value);
+  }
+
+  function transferableTokens(address holder, uint64 time) constant public returns (uint256) {
+    return balanceOf(holder);
+  }
+}