remove unneccessary bootstrap css and js. close #275
minor change.
add cohort analysis. #close 268
remove therubyracer gem.
Merge pull request #278 from saberma/saberma-enhancement/remove-therubyracer-gem

去掉 therubyracer gem.
update deploy config.
add daemons gem for delayed job.
add nginx config template.
[deploy]fixed host missing.
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.
update invitation email content.
Merge pull request #281 from saberma/saberma-enhancement/add-alpha-logo-label

加入 alpha label
fixed rspec error.
Merge branch 'master' of github.com:saberma/19wu