Add solc 5 to AttributeRegistryInterface's pragma

Allow AttributeRegistryInterface to be used by Solidity 5 projects as well.

Author: HardlyDifficult

contracts/AttributeRegistryInterface.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.25;
+pragma solidity >=0.4.25;
 
 
 /**
@@ -52,4 +52,4 @@ interface AttributeRegistryInterface {
  * `index` value falls inside said range.
  */
  function getAttributeTypeID(uint256 index) external view returns (uint256);
-}
+}