Likes: display below excerpts as well

Before this commit, Likes were only displayed below the_content
Sharing buttons, on the other hand, are displayed everywhere

Both modules should have the same behaviour
Likes: do not hide Likes for excerpts

See #484
Likes: remove $wp_current_filter

It's not necessary anymore now that we don't check for excerpts
Merge pull request #484 from jeherve/likes-excerpt

Likes: display below excerpts as well