add note about Counters rename in changelog (#1703)

CHANGELOG.md

@@ -18,14 +18,14 @@
  * Upgraded the minimum compiler version to v0.5.2: this removes many Solidity warnings that were false positives. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
  * `ECDSA`: `recover` no longer accepts malleable signatures (those using upper-range values for `s`, or 0/1 for `v`). ([#1622](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1622))
  * `ERC721`'s transfers are now more gas efficient due to removal of unnecessary `SafeMath` calls. ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
- * `Counter`'s API has been improved, and is now used by `ERC721` (though it is still in `drafts`). ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
  * Fixed variable shadowing issues. ([#1606](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1606))
 
 ### Bugfixes:
  * (minor) `SafeERC20`: `safeApprove` wasn't properly checking for a zero allowance when attempting to set a non-zero allowance. ([#1647](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1647))
 
-### Breaking changes:
- * `TokenMetadata` (in drafts) has been renamed to `ERC20Metadata`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
+### Breaking changes in drafts:
+ * `TokenMetadata` has been renamed to `ERC20Metadata`. ([#1618](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1618))
+ * The library `Counter` has been renamed to `Counters` and its API has been improved. See an example in `ERC721`, lines [17](https://github.com/OpenZeppelin/openzeppelin-solidity/blob/3cb4a00fce1da76196ac0ac3a0ae9702b99642b5/contracts/token/ERC721/ERC721.sol#L17) and [204](https://github.com/OpenZeppelin/openzeppelin-solidity/blob/3cb4a00fce1da76196ac0ac3a0ae9702b99642b5/contracts/token/ERC721/ERC721.sol#L204). ([#1610](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1610))
 
 ## 2.1.3 (2019-02-26)
  * Backported `SafeERC20.safeApprove` bugfix. ([#1647](https://github.com/OpenZeppelin/openzeppelin-solidity/pull/1647))