Jekyll v3.1.0.pre.beta1 发布静态站点生成器

Jekyll v3.1.0.pre.beta1 发布，此版本改进内容：

Use Liquid::Drops instead of Hashes in #to_liquid (#4277)
Add ‘sample’ Liquid filter Equivalent to Array#sample functionality (#4223)
Cache parsed include file to save liquid parsing time. (#4120)
Slightly speed up url sanitization and handle multiples of ///. (#4168)
Print debug message when a document is skipped from reading (#4180)
Include tag should accept multiple variables in the include name (#4183)
Add -o option to serve command which opens server URL (#4144)
Add CodeClimate platform for better code quality. (#4220)
General improvements for WEBrick via jekyll serve such as SSL & custom headers (#4224,#4228)
Add a default charset to content-type on webrick. (#4231)
Switch PluginManager to use require_with_graceful_fail for better UX (#4233)
Allow quoted date in front matter defaults (#4184)
Add a Jekyll doctor warning for URLs that only differ by case (#3171)
drops: create one base Drop class which can be set as mutable or not (#4285)
drops: provide #to_h to allow for hash introspection (#4281)