add efficient filesystem handling for guard
Revert "add efficient filesystem handling for guard"

This reverts commit 6ba615c5866021a30d6b2c50ae33044b180dd14b.
Merge branch 'official'
Merge branch 'official'
Merge branch 'official'
翻译了部分文档，请进一步完善
Merge remote-tracking branch 'richard-ma/master' into translation/en
add homepage feature description. close #320
Merge pull request #335 from saberma/saberma-enhancement/320-homepage-describe-slug-and-follow-feature

首页增加特色描述 #320
event display end. fix #330
Merge remote-tracking branch 'upstream/master' into feature/330-event-display-end
event display end 2.fix #330
Merge pull request #328 from saberma/translation/en

英文版本翻译
Merge pull request #338 from ebowsoft/feature/330-event-display-end

event display end. fix #330
it should return to event page after sign in. fixed #339
merge.
use sendgrid.
config exception recipients.
Fixed heroku error, Gemfile.lock is ignore, slim version don't match:

ActionView::Template::Error (Unexpected text indentation
  /app/app/views/layouts/application.html.slim, Line 14
      header#header
      ^
fixed travis-ci error.