Add some attributes

Add FreezeZone: the specified area cannot display content
maxContentWidth: limits the maximum width of the text, only horizontally
minContentMargin: Forces the description text to be separated by a corresponding distance

Refactoring the code to define the properties of each element separately, retaining the features of the previous version

1.2.0

Update EasyStepIndicator.podspec

This is the last version of the restricted node that can only be text

最后一版,节点仅为文字描述
从下一版开始,加入自定义View,也就是每个节点的View能够自定义