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/math/Math.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.0;
 
 /**
  * @title Math

contracts/math/SafeMath.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.4.24;
+pragma solidity ^0.5.0;
 
 /**
  * @title SafeMath