add site search
Chained `replace` calls

- Remove `https`, then `http`
Added sidebar image. Disable RSS feed link in navigation bar if neither of FEED_RSS or FEED_ATOM is specified.
Removed superfluous tags from sidebar image section

The sidebar image is positioned too close to the "show/hide sidebar control". I put some tags there that introduced an empty space, to push the sidebar image downwards. However, the "right way" to manage that space is through CSS. So in this commit, I removed said tags to make the code cleaner.
Merge pull request #36 from sagarbehere/navbarimg_rssfix

Add sidebar author's image and make atom feed optional.
minor changes to the doc and add contributors ref
Added SITENAME to page template
Replace RSS with Atom on navigation bar while it is Atom
Social plugin only shows RSS/Atom feeds if available
Merge pull request #38 from xr09/master

Added SITENAME to page template
Merge pull request #42 from nhanb/conditional-feed-links

Social plugin only shows RSS/Atom feeds if available
Merge pull request #39 from changyuheng/pr_fix_atom_typo

Replace RSS with Atom on navigation bar while it is Atom
Merge pull request #27 from nt3rp/add-search-box

Add site search settings