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

This reverts commit 6ba615c5866021a30d6b2c50ae33044b180dd14b.
Merge branch 'official'
Merge branch 'official'
remove unneccessary bootstrap css and js. close #275
add cohort analysis. #close 268
add nginx config template.
serve /uploads
fixed rspec error.
merge.
Merge pull request #276 from saberma/saberma-enhancement/275-remove-unneccessary-css-and-js

删除不需要的 bootstrap css 和 js
Merge pull request #279 from saberma/saberma-enhancement/add-nginx-config-template

加入 nginx 配置模板
add alpha logo label.
add `bootstrap-timepicker-rails` gem
add bootstrap-timepicker-rails needs js and css require code
used bootstrap-timepicker to show time
add some test code with verify the modified
update invitation email content.
Merge pull request #281 from saberma/saberma-enhancement/add-alpha-logo-label

加入 alpha label
fixed rspec error.