add devise gem
add devise & user model
convert erb to slim
convert users erb to slime
convert devise erb to slim
temp
Issue #40 - 去除在Gemfile中对RSpec的声明（rspec-rail会自动安装依赖）
同时清理了Gemfile的代码，看着清爽，也对初学者更友好一些。
Merge branch 'master' into feature/13-user-sign-up

Conflicts:
	Gemfile.lock
实现首页用户注册 refs #13
修改确认密码placeholder refs #13
将昵称改为登录名，nickname -> login refs #13 #67
fix time zone issue
Get rid of ruby-head since it will cause timeout in Travis
Change Timezone to 'Beijing'(UTC +8)
So, now if you type Time.zone.nowin Rails console, you'll see the
correct time in UTC +8
add CHANGELOG, refs #68
Add link to see all contributors in README, refs #68
add CONTRIBUTING.md, refs #68
change log for oss manifesto
clear codebase
将index表单使用helper实现 ref #13