Updated Rakefile.

Rakefile now creates new posts with a default description of "false."
It was previously an empty string, which would hide the index version of
the post entirely.

Signed-off-by: Byron Sanchez <bfs5030@gmail.com>
Added the initial version of the pagination plugin.

The pagination plugin allows you to replace the default Jekyll
"page.previous" and "page.next" links with more flexible links. You can
hide some pages from the pager timeline, or you can use a category
filter.

Signed-off-by: Byron Sanchez <bfs5030@gmail.com>