chore: remove babel, fix integration tests

This commit removes babel/es6 from all source and test files, because it was introducing a lot of overhead and only little gain.
This commit fixes and enables integration tests on Travis.
This commit fixes #153 and #151 along the way.

_Originally this commit should have only removed babel, but without working tests that's a bit too hairy._
_I only realized that half way into removing babel/es6, so things are all over the place now._

Closes #153, Closes #151

test/lib/base-scenario.js

@@ -1,4 +1,4 @@
-const nixt = require('nixt')
+var nixt = require('nixt')
 
 module.exports = function (cwd, uri) {
   return nixt()
@@ -7,8 +7,6 @@ module.exports = function (cwd, uri) {
 		.env('NPM_EMAIL', 'integration@test.com')
     .env('GH_TOKEN', 'ghtoken')
     .env('CI', 'true')
-    .env('TRAVIS', 'true')
-    .env('TRAVIS_BRANCH', 'master')
     .env('npm_config_registry', uri)
     .clone()
 }

test/lib/test-module.js

@@ -1,40 +1,31 @@
-const { exec } = require('child_process')
-const { join } = require('path')
-const { writeFileSync } = require('fs')
+var exec = require('child_process').exec
+var join = require('path').join
+var writeFileSync = require('fs').writeFileSync
 
-const mkdirp = require('mkdirp')
+var mkdirp = require('mkdirp')
 
-module.exports = function (name, cb) {
-  const cwd = join(__dirname, '../tmp', name)
+module.exports = function (name, registry, cb) {
+  var cwd = join(__dirname, '../tmp', name)
 
   mkdirp.sync(cwd)
 
-  writeFileSync(join(cwd, '.npmrc'), `
-//localhost:1337/registry/_design/app/_rewrite/:username=integration
-//localhost:1337/registry/_design/app/_rewrite/:email=integration@test.com`, null, 2)
-
   writeFileSync(join(cwd, 'package.json'), JSON.stringify({
-    name,
+    name: name,
     repository: {
       url: 'git+https://github.com/semantic-release/test'
     },
-    _npmUser: {
-      name: 'integration',
-      email: 'integration@test.com'
-    },
-    maintainers: [{
-      name: 'integration',
-      email: 'integration@test.com'
-    }]
+    release: {
+      verifyConditions: '../../../src/lib/plugin-noop'
+    }
   }, null, 2))
 
-  exec(`
-    git init &&
-    git config user.email "integration@test" &&
-    git config user.name "Integration Test" &&
-    git add . &&
-    git commit -m "chore: root"`
-  , {cwd}, (err, stdout, stderr) => {
+  exec(
+  'git init && ' +
+  'git config user.email "integration@test" && ' +
+  'git config user.name "Integration Test" && ' +
+  'git add . && ' +
+  'git commit -m "chore: root"'
+  , {cwd: cwd}, function (err, stdout, stderr) {
     if (err) {
       console.log(stdout, stderr)
       return cb(err)