Fix Jekyll 1.1 pagination incompatibility

* Jekyll 1.1 introduces a bug fix which breaks the pagination.rb plugin
  in Octopress. When the user does a "jekyll build" or "jekyll serve" from
  the console, an error message will appear for "wrong number of arguments (2 for 1)"
  on the method call pagination_enabled?

* Changes in this commit mirror the jekyll commit:

https://github.com/jekyll/jekyll/commit/bd0e45c1b9b3bd8c51ddc64d5909c2c413dab165