Transition from buidler to hardhat

package.json

@@ -9,8 +9,8 @@
     "/test/behaviors"
   ],
   "scripts": {
-    "compile": "buidler compile",
-    "coverage": "buidler coverage",
+    "compile": "hardhat compile",
+    "coverage": "hardhat coverage",
     "docs": "oz-docs",
     "docs:watch": "npm run docs watch contracts 'docs/*.hbs'",
     "prepare-docs": "scripts/prepare-docs.sh",
@@ -24,7 +24,7 @@
     "prepack": "scripts/prepack.sh",
     "release": "scripts/release/release.sh",
     "version": "scripts/release/version.sh",
-    "test": "buidler test"
+    "test": "hardhat test"
   },
   "repository": {
     "type": "git",
@@ -45,9 +45,9 @@
   },
   "homepage": "https://openzeppelin.com/contracts/",
   "devDependencies": {
-    "@nomiclabs/buidler": "^1.4.8",
-    "@nomiclabs/buidler-truffle5": "^1.3.4",
-    "@nomiclabs/buidler-web3": "^1.3.4",
+    "@nomiclabs/hardhat-solhint": "^2.0.0",
+    "@nomiclabs/hardhat-truffle5": "^2.0.0",
+    "@nomiclabs/hardhat-web3": "^2.0.0",
     "@openzeppelin/docs-utils": "^0.1.0",
     "@openzeppelin/gsn-helpers": "^0.2.3",
     "@openzeppelin/gsn-provider": "^0.1.10",
@@ -63,6 +63,7 @@
     "eth-sig-util": "^3.0.0",
     "ethereumjs-util": "^7.0.7",
     "ethereumjs-wallet": "^1.0.1",
+    "hardhat": "^2.0.6",
     "lodash.startcase": "^4.4.0",
     "lodash.zip": "^4.2.0",
     "micromatch": "^4.0.2",