update liquid in sidebar.html to avoid mutliple entries for paginated resources

[flyinggrizzly]

Previously the template would generate multiple sidebar links to the same section if that section used layout: page and was paginated (i.e. blogs).

Liquid now checks if the url of the node it is parsing contains 'page*', and if so, skips it. It will now only pick up the index.html files with layout: page

[agude]

I just ran into this issue! Thanks for the PR, it let me fix it on my site.