label 设置：
- numberOfLines = 0；
2.[label sizeToFit];
3.label.preferredMaxLayoutWidth = xxx;
[label mas_makeConstraints:^(MASConstraintMaker *make) {
make.edges.mas_equalTo(0);
}];
[view mas_makeConstraints:^(MASConstraintMaker *make) {
make.left.top.mas_equalTo(0);
}];
