fair 0.2.0+3

Flutter Fair is a package used to update widget tree dynamically.

[0.2.0+3]

• Remove some api for v1.12.13 to avoid compile issue.

[0.2.0+2]

• add Sugar.mapEach support in build method.

[0.2.0+1]

• Support widget update through local assets and remote uri.
• Compact with flutter v1.22.4, v1.20.4, v1.17.3, v1.12.13.
• Generate bundle with build_runner.
• Add state binding for FairWidget
• Support partial refresh of FairWidget