Optimization code
[#348] display event history on event show page
[#348] add related spec
[#348] add I18n support
followers fix #340
test code for followers #340
[#348] Refactor: move view related method to help module, also moving related spec
Merge pull request #351 from loveky/master

#348 显示往期活动记录
[#357] add link to event edit page in event show page
merge.