v4.1.1

What's Changed

• YouTube埋め込みではないiframeで高さの調整を行わないようにする by @sanographix in #13
• Gulp4 by @sanographix in #14
• Fix image aspect ratio by @sanographix in #15
• change twitter icon by @sanographix in #18

Full Changelog: v4.1.0...v4.1.1