Update Compiler Version to 0.5.0

[relyt29]

Update the compiler version for the Auction Example to 0.5.0 so we can use abi.decode. Currently not possible until the OpenZeppelin folks update their code to use the newer compiler version. On-hold, but should be an easy change

openzeppelin-solidity/contracts/access/roles/MinterRole.sol:1:1: SyntaxError: Source file requires different compiler version (current compiler is 0.5.0+commit.1d4f565a.Linux.g++ - note that nightly builds are considered to be strictly less than the released version
pragma solidity ^0.4.24;
^----------------------^

[nventuro]

Hi, @nventuro from OpenZeppelin here! Just a heads up, we've just released the 2.1 release candidate, and plan to release a version supporting Solidity 0.5.x as well over the coming days, so stay tuned!

[lorenzb]

proveth and openzeppelin are both at 0.5.0, so we should be good to go ahead.