Inherit Ownable in Migrations and Killable. Fix naming convention.

contracts/Killable.sol

@@ -6,7 +6,7 @@ import "./Ownable.sol";
  * Base contract that can be killed by owner
  */
 contract Killable is Ownable {
-  function kill() {
-    if (msg.sender == owner) selfdestruct(owner);
+  function kill() onlyOwner {
+    selfdestruct(owner);
   }
 }

contracts/Migrations.sol

@@ -1,22 +1,13 @@
 pragma solidity ^0.4.4;
-contract Migrations {
-  address public owner;
-  uint public last_completed_migration;
+contract Migrations is Ownable {
+  uint public lastCompletedMigration;
 
-  modifier restricted() {
-    if (msg.sender == owner) _;
+  function setCompleted(uint completed) onlyOwner {
+    lastCompletedMigration = completed;
   }
 
-  function Migrations() {
-    owner = msg.sender;
-  }
-
-  function setCompleted(uint completed) restricted {
-    last_completed_migration = completed;
-  }
-
-  function upgrade(address new_address) restricted {
-    Migrations upgraded = Migrations(new_address);
-    upgraded.setCompleted(last_completed_migration);
+  function upgrade(address newAddress) onlyOwner {
+    Migrations upgraded = Migrations(newAddress);
+    upgraded.setCompleted(lastCompletedMigration);
   }
 }