SafeMath is now more consistent with itself. (#1168)

contracts/math/SafeMath.sol

@@ -10,7 +10,7 @@ library SafeMath {
   /**
   * @dev Multiplies two numbers, throws on overflow.
   */
-  function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
+  function mul(uint256 _a, uint256 _b) internal pure returns (uint256) {
     // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
     // benefit is lost if 'b' is also tested.
     // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
@@ -18,8 +18,9 @@ library SafeMath {
       return 0;
     }
 
-    c = _a * _b;
+    uint256 c = _a * _b;
     assert(c / _a == _b);
+
     return c;
   }
 
@@ -28,9 +29,10 @@ library SafeMath {
   */
   function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
     // assert(_b > 0); // Solidity automatically throws when dividing by 0
-    // uint256 c = _a / _b;
+    uint256 c = _a / _b;
     // assert(_a == _b * c + _a % _b); // There is no case in which this doesn't hold
-    return _a / _b;
+
+    return c;
   }
 
   /**
@@ -38,15 +40,18 @@ library SafeMath {
   */
   function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
     assert(_b <= _a);
-    return _a - _b;
+    uint256 c = _a - _b;
+
+    return c;
   }
 
   /**
   * @dev Adds two numbers, throws on overflow.
   */
-  function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
-    c = _a + _b;
+  function add(uint256 _a, uint256 _b) internal pure returns (uint256) {
+    uint256 c = _a + _b;
     assert(c >= _a);
+
     return c;
   }
 }