[BUGFIX] Prevent PageNotFound exception by paginate widget

If the current page's node has no Posts set at all,
the paginate widget will throw a Page Not Found exception
as if there were no additional posts on some subsequent
page; but this happens also on the initial call.

This patch circumvents this behavior with checking
if there are any posts at all, prior to invoking
the paginate widget.

Fixes #2
[FEATURE] Expand readme with a quick start

This adds some lines how to get really started
with the blog plugin.

Closes #1
Merge pull request #3 from afoeder/master

Commits for issues 1 and 2