upgrade to solidity 0.6.8 (#106)

.solhint.json

@@ -3,6 +3,6 @@
   "rules": {
     "indent": [4],
     "not-rely-on-time": "off",
-    "mark-callable-contracts": "off"
+    "compiler-version": "off"
   }
 }

Dockerfile.abigen

@@ -1,7 +1,7 @@
 FROM node:10.16.0-stretch as builder
 
 ARG GETH_VERSION="1.9.7-a718daa6"
-ARG SOLIDITY_VERSION="0.5.15"
+ARG SOLIDITY_VERSION="0.6.8"
 
 RUN wget -q "https://github.com/ethereum/solidity/releases/download/v$SOLIDITY_VERSION/solc-static-linux" \
   && chmod +x solc-static-linux \

README.md

@@ -19,9 +19,8 @@ To also generate coverage information use `npm run coverage` instead.
 
 ## Linting
 
-This repo currently uses both `solhint` and `ethlint` as linters. Both can be called through npm:
+This repo currently uses `solhint` as linter. It can be called through npm:
 ```sh
-npm run ethlint
 npm run solhint
 ```
 

contracts/ERC20SimpleSwap.sol

@@ -1,8 +1,8 @@
-pragma solidity =0.5.15;
+pragma solidity =0.6.8;
 import "@openzeppelin/contracts/math/SafeMath.sol";
 import "@openzeppelin/contracts/math/Math.sol";
 import "@openzeppelin/contracts/cryptography/ECDSA.sol";
-import "@openzeppelin/contracts/token/ERC20/ERC20Mintable.sol";
+import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
 
 /**
 @title Chequebook contract without waivers

contracts/Migrations.sol

@@ -1,4 +1,5 @@
-pragma solidity ^0.5.0;
+pragma solidity =0.6.8;
+import "@openzeppelin/contracts/presets/ERC20PresetMinterPauser.sol";
 
 contract Migrations {
   address public owner;

contracts/SimpleSwapFactory.sol

@@ -1,4 +1,4 @@
-pragma solidity =0.5.15;
+pragma solidity =0.6.8;
 import "./ERC20SimpleSwap.sol";
 
 /**