build: use npm instead of Grunt

Except for updating contributors, which remains in Grunt.

#243

gruntfile.js

@@ -1,80 +1,11 @@
 module.exports = function (grunt) {
+  grunt.loadNpmTasks('grunt-npm')
   grunt.initConfig({
     pkgFile: 'package.json',
-    simplemocha: {
-      options: {
-        ui: 'bdd',
-        reporter: 'dot'
-      },
-      unit: {
-        src: [
-          'test/mocha-globals.js',
-          'test/*.spec.js'
-        ]
-      }
-    },
     'npm-contributors': {
       options: {
         commitMessage: 'chore: update contributors'
       }
-    },
-    conventionalChangelog: {
-      release: {
-        options: {
-          changelogOpts: {
-            preset: 'angular'
-          }
-        },
-        src: 'CHANGELOG.md'
-      }
-    },
-    conventionalGithubReleaser: {
-      release: {
-        options: {
-          auth: {
-            type: 'oauth',
-            token: process.env.GH_TOKEN
-          },
-          changelogOpts: {
-            preset: 'angular',
-            releaseCount: 0
-          }
-        }
-      }
-    },
-    bump: {
-      options: {
-        commitMessage: 'chore: release v%VERSION%',
-        pushTo: 'upstream',
-        commitFiles: [
-          'package.json',
-          'CHANGELOG.md'
-        ]
-      }
-    },
-    karma: {
-      options: {
-        singleRun: true
-      },
-      simple: {
-        configFile: 'examples/simple/karma.conf.js'
-      }
     }
   })
-
-  require('load-grunt-tasks')(grunt)
-
-  grunt.registerTask('test', ['simplemocha'])
-  grunt.registerTask('default', ['test'])
-
-  grunt.registerTask('release', 'Bump the version and publish to NPM.', function (type) {
-    grunt.task.run([
-      'npm-contributors',
-      'bump:' + (type || 'patch') + ':bump-only',
-      'conventionalChangelog',
-      'bump-commit',
-      'conventionalGithubReleaser',
-      'npm-publish'
-    ])
-  })
 }