Update CHANGELOG for version 2.7.1
Update CHANGELOG for version 2.7.1

mingsai/XCDYouTubeVideoPlayerViewController,mingsai/XCDYouTubeVideoPlayerViewController,mingsai/XCDYouTubeVideoPlayerViewController,twobitlabs/XCDYouTubeKit,creationst/XCDYouTubeKit,creationst/XCDYouTubeKit,twobitlabs/XCDYouTubeKit,mingsai/XCDYouTubeVideoPlayerViewController,twobitlabs/XCDYouTubeKit,creationst/XCDYouTubeKit,twobitlabs/XCDYouTubeKit,0xced/XCDYouTubeKit,0xced/XCDYouTubeKit,0xced/XCDYouTubeKit,0xced/XCDYouTubeKit,creationst/XCDYouTubeKit