Upgrade to Material-UI v4

package.json

 {
     "name": "@gsc/material",
-    "version": "1.1.0",
+    "version": "2.0.0",
     "description": "An implementation of Material-UI with GSC styling",
     "main": "index.js",
-    "repository": "https://git.gsc.org.uk/utils/gsc-material.git",
+    "repository": "https://gitlab.gsc.org.uk/gsc-frameworks/gsc-material.git",
     "author": "Ben Galloway <ben.galloway@gsc.org.uk>",
     "license": "MIT",
     "private": true,
@@ -12,7 +12,7 @@
         "ProximaNovaFontFace.css"
     ],
     "peerDependencies": {
-        "@material-ui/core": "^3.3.0"
+        "@material-ui/core": "^4.1.0"
     },
     "devDependencies": {
         "@babel/cli": "^7.1.2",

src/index.js

 import React from "react";
-import { MuiThemeProvider, createMuiTheme } from "@material-ui/core/styles";
+import { MuiThemeProvider, createMuiTheme, responsiveFontSizes } from "@material-ui/core/styles";
 import { CssBaseline } from "@material-ui/core";
 
-const GSCTheme = createMuiTheme({
+const GSCTheme = responsiveFontSizes(
+    createMuiTheme({
+        gsc: {
+            // Core
+            navy: "#2e2d44",
+            teal: "#30b7bb",
+            offwhite: "#f1f4f5",
+            // Secondary
+            pink: "#e12a58",
+            gold: "#e5b94c",
+            // Tertiary
+            darkteal: "#036173",
+            blue: "#36a9e1",
+            lime: "#d5db40",
+            orange: "#e56a0c",
+            red: "#e40426",
+            purple: "#64335f",
+            green: "#22b573",
+            white: "#ffffff",
+        },
         palette: {
             primary: {
-            main: "#2e2d44",
-            contrastText: "#f1f4f5",
+                main: theme.gsc.navy,
+                contrastText: theme.gsc.offwhite,
             },
             secondary: {
-            main: "#30b7bb",
-            contrastText: "#2e2d44",
+                main: theme.gsc.teal,
+                contrastText: theme.gsc.navy,
             },
             error: {
-            main: "#e40426",
+                main: theme.gsc.red,
             },
             background: {
-            default: "#f1f4f5",
-            paper: "#ffffff",
+                default: theme.gsc.offwhite,
+                paper: theme.gsc.white,
             },
         },
         typography: {
-        useNextVariants: true,
             fontFamily: [
                 '"Helvetica Neue"',
                 "Arial",
@@ -60,11 +78,9 @@ const GSCTheme = createMuiTheme({
             button: {
                 textTransform: "none",
             },
-        buttonNext: {
-            textTransform: "none",
-        },
         },
-});
+    })
+);
 
 const GSCMaterial = props => (
     <MuiThemeProvider theme={GSCTheme}>