[new] Motified to Fastnlp/io/pipe/summarization.py for Summarization/Baseline

[dqwang122]

Description：简要描述这次PR的内容

Main reason: 做出这次修改的原因

Checklist 检查下面各项是否完成

Please feel free to remove inapplicable items for your PR.

• [ ] The PR title starts with [$CATEGORY] (例如[bugfix]修复bug，[new]添加新功能，[test]修改测试，[rm]删除旧代码)
• [ ] Changes are complete (i.e. I finished coding on this PR) 修改完成才提PR
• [ ] All changes have test coverage 修改的部分顺利通过测试。对于fastnlp/fastnlp/的修改，测试代码必须提供在fastnlp/test/。
• [ ] Code is well-documented 注释写好，API文档会从注释中抽取
• [ ] To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change 修改导致例子或tutorial有变化，请找核心开发人员

Changes: 逐项描述修改的内容

• 添加了新模型；用于句子分类的CNN，来自Yoon Kim的Convolutional Neural Networks for Sentence Classification
• 修改dataset.py中过时的和不合规则的注释 #286
• 添加对var-LSTM的测试代码

Mention: 找人review你的PR

@修改过这个文件的人 @核心开发人员

[codecov-io]

Codecov Report

Merging #224 into dev0.5.0 will increase coverage by 5.1%. The diff coverage is 88.78%.

@@            Coverage Diff             @@
##           dev0.5.0    #224     +/-   ##
==========================================
+ Coverage      70.8%   75.9%   +5.1%     
==========================================
  Files            80      81      +1     
  Lines          9345    9717    +372     
==========================================
+ Hits           6617    7376    +759     
+ Misses         2728    2341    -387

Impacted Files	Coverage Δ
fastNLP/io/loader/json.py	95.83% <ø> (ø)	:arrow_up:
fastNLP/io/pipe/summarization.py	88.78% <88.78%> (ø)
fastNLP/models/snli.py	91.48% <0%> (-1.79%)	:arrow_down:
fastNLP/modules/__init__.py	100% <0%> (ø)	:arrow_up:
fastNLP/modules/encoder/__init__.py	100% <0%> (ø)	:arrow_up:
fastNLP/core/trainer.py	77.31% <0%> (+0.25%)	:arrow_up:
fastNLP/core/dataset.py	81.34% <0%> (+0.91%)	:arrow_up:
fastNLP/core/field.py	71.09% <0%> (+1.15%)	:arrow_up:
fastNLP/io/data_bundle.py	62.2% <0%> (+2.36%)	:arrow_up:
... and 19 more

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