pin_input_text_field 0.1.0

A textField widget to help display different style pin

[0.0.1] - 2018/12/24.

• first commit.

[0.1.0] - 2019/01/09

• add comment to help understand source code.
• add obscure style to be more customize.
• add onPinChanged to observe the text changed.
• add solidColor to set background color in BoxLooseDecoration & BoxTightDecoration
• add enteredColor for UnderlineDecoration&BoxLooseDecoration
• remove const default variable in PinInputTextField.
• fix wrong place in painting