Merge branch 'hotfix/README'
Merge commit 'bd22608fc76bc7a29e8ce35f0598e58161c1ac80'
Merge commit 'd3c3aa16f4bdf3888f700c55fc62375a28f9d944'

Conflicts:
	Vocabulary.xcodeproj/project.pbxproj
	Vocabulary/AppDelegate.m
Merge branch 'release/3.1.0_beta2'

Conflicts:
	Vocabulary/AppDelegate.m
Merge branch 'release/3.1.0_beta3'
Merge branch 'release/3.1.1_alpha1'
Merge branch 'release/3.1.1_beta1'
Merge branch 'release/3.1.1_alpha2'
Merge branch 'release/3.1.1_alpha3'
重命名一些方法
使用PromiseKit
修改一处崩溃
注释掉无用的代码
可选择测试模式
Merge branch 'feature/exam_improvement' into develop
修改一些图片
修改熟悉度计算
Merge branch 'release/3.1.1_alpha4'
modify read
Merge branch 'hotfix/readme_modification' into develop