Fix Post-rendering bug

Ember.Handlebars.normalizePath was being called with an object as
argument which caused it to error out.
also wrapped the return in a SafeString, so the html will not get
escaped again.
Merge pull request #1822 from cfstras/breakUp_username_fix

Fix Post-rendering bug
BUGFIX: more robust breakUp helper
Posts by trust level 3 users do not have nofollow on their external links.
FEATURE: overridable template for adding custom buttons on the composer
FEATURE: 2x the default number of topics showed in the top page
Admins don't see uncategorized on /categories if it has no topics and allow_uncategorized_topics is false
Don't show uncategorized in hamburger menu if it's empty, unless you're staff
BUGFIX: only show the best period for logged-in users
Staff can create uncategorized topics even if allow_uncategorized_topics is false
rename topics_per_period_in_summary settings to topics_per_period_in_top_summary
FEATURE: top page should not be infinite. Limite them to 200 topics by default
mention "privately" in flagging dialog
a bit more private cue on flag tooltip
BUGFIX: exclude categories from the top view
BUGFIX: use previous_visit_at instead of last_seen_at to determine the best period to display in the top summary
Merge remote-tracking branch 'upstream/master'