Revert "Switch to babel 6"

scripts/babelcheck.js

@@ -1,22 +0,0 @@
-#!/usr/bin/env node
-
-var exec = require('child_process').exec;
-
-// Makes sure the babel executable in the path is babel 6 (or greater), not
-// babel 5, which it is if you upgrade from an older version of react-sdk and
-// run 'npm install' since the package has changed to babel-cli, so 'babel'
-// remains installed and the executable in node_modules/.bin remains as babel
-// 5.
-
-exec("babel -V", function (error, stdout, stderr) {
-    if ((error && error.code) || parseInt(stdout.substr(0,1), 10) < 6) {
-        console.log("\033[31m\033[1m"+
-            '*****************************************\n'+
-            '* matrix-react-sdk has moved to babel 6 *\n'+
-            '* Please "rm -rf node_modules && npm i" *\n'+
-            '* then restore links as appropriate     *\n'+
-            '*****************************************\n'+
-        "\033[91m");
-        process.exit(1);
-    }
-});