Add paginate plugin; Update gems.

[lucazz]

Esse PR resolve dois problemas:

1) atualiza algumas gems, em especial a gem yajl-ruby, que tem uma vulnerabilidade publicada e que nois foi apontado pelo proprio gh:

2) Adiciona o plugin de paginação do Jekyll:

Por favor, testem localmente também, não tive tempo de testar tudo.

bb-8 _posts (update-gems) $ bundle exec jekyll serve
Configuration file: none
            Source: /Users/Lucas/Library/Mobile Documents/com~apple~CloudDocs/Projects/Ruby/guru-ce.github.io/_posts
       Destination: /Users/Lucas/Library/Mobile Documents/com~apple~CloudDocs/Projects/Ruby/guru-ce.github.io/_posts/_site
 Incremental build: disabled. Enable with --incremental
      Generating...
     Build Warning: Layout 'post' requested in 2014-10-02-contribuir-com-o-guruce.md does not exist.
     Build Warning: Layout 'post' requested in 2015-03-10-decimo-quarto-encontro-guruce.md does not exist.
     Build Warning: Layout 'post' requested in 2015-04-07-decimo-quinto-encontro-guruce.md does not exist.
     Build Warning: Layout 'post' requested in 2015-05-19-decimo-sexto-encontro-guruce.md does not exist.
     Build Warning: Layout 'post' requested in 2015-06-23-trabalho-remoto-hangout.md does not exist.
     Build Warning: Layout 'post' requested in 2015-07-02-decimo-setimo-encontro-guruce.md does not exist.
     Build Warning: Layout 'post' requested in 2015-07-03-slack-do-guru.md does not exist.
     Build Warning: Layout 'post' requested in 2015-09-01-ruby-conf-br.md does not exist.
     Build Warning: Layout 'post' requested in 2015-09-23-decimo-oitavo-encontro-guruce.md does not exist.
     Build Warning: Layout 'post' requested in 2015-12-04-primeiro-encontro-guruce-2016.md does not exist.
     Build Warning: Layout 'post' requested in 2016-07-06-agradecimento-technically-speaking.md does not exist.
     Build Warning: Layout 'post' requested in 2016-09-19-vigesimo-encontro.md does not exist.
     Build Warning: Layout 'post' requested in 2016-10-06-errata-encontro-20.md does not exist.
     Build Warning: Layout 'post' requested in 2017-02-14-vigesimo-primeiro-encontro.md does not exist.
     Build Warning: Layout 'post' requested in 2017-10-02-vigesimo-segundo-encontro.md does not exist.
                    done in 0.109 seconds.
 Auto-regeneration: enabled for '/Users/Lucas/Library/Mobile Documents/com~apple~CloudDocs/Projects/Ruby/guru-ce.github.io/_posts'
    Server address: http://127.0.0.1:4000
  Server running... press ctrl-c to stop.

[lucazz]

Testei agora aqui, ta tendo um comportamento meio tosco, vou resolver isso mastarde.

[herminiotorres]

resolvido!