Release v2.1.0 solc 0.5.x (#1568)

* Now compiling in a separate directory using truffle 5.

* Ported to 0.5.1, now compiling using 0.5.1.

* test now also compiles using the truffle 5 hack.

* Downgraded to 0.5.0.

* Sorted scripts.

* Cleaned up the compile script a bit.

contracts/drafts/ERC1046/TokenMetadata.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.0;
 
 import "../../token/ERC20/IERC20.sol";
 
@@ -9,17 +9,17 @@ import "../../token/ERC20/IERC20.sol";
  * @dev TODO - update https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/token/ERC721/IERC721.sol#L17 when 1046 is finalized
  */
 contract ERC20TokenMetadata is IERC20 {
-    function tokenURI() external view returns (string);
+    function tokenURI() external view returns (string memory);
 }
 
 contract ERC20WithMetadata is ERC20TokenMetadata {
     string private _tokenURI;
 
-    constructor (string tokenURI) public {
+    constructor (string memory tokenURI) public {
         _tokenURI = tokenURI;
     }
 
-    function tokenURI() external view returns (string) {
+    function tokenURI() external view returns (string memory) {
         return _tokenURI;
     }
 }