Added 'SmartCase' matcher to default matchers

Hi, peco developers.

I implemented `SmartCase` matcher to realize smart-case matching on peco.

![ss](http://gifzo.net/BMXVZDL6wPW.gif)

Smart-case matching is very popular and useful, which is implemented bash, zsh, vim and so on.  I love the matching and eager to add it to peco.