更新f2到3.3.8，添加f2新增的plugin pieLabel和带文本饼图labelline-pie#3449

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WilliamLin1990 wants to merge 4 commits intoairyland:v2from

WilliamLin1990:f2

Commits on Oct 19, 2016

unicode转义字符的前缀应该是'\u'
qsjia
authored

Commits on Jan 20, 2017

Merge pull request #629 from qsjia/patch-1
airyland
authored

Commits on Apr 17, 2019