Bump favcount.js to v1.5.0

We've already made the CORS changes in our copy of favcount, but we
should bump the version to match upstream.
Merge pull request #1855 from chrishunt/update-favcount

Bump favcount.js to v1.5.0
FIX: Show "Begin Discussion" button when there are 0 replies
FIX: Show category text color in oneboxes
Adds unit tests for SearchController
Adds new QUnit assertion ("not") complementary to built-in "ok"
Don't seed a welcome topic on every db:migrate
FEATURE: add a 14 days window to consider topics new
Update the OS X development documentation

* Remove some outdated information from the guide
* Add scripts/osx_dev to bootstrap a working development environment
* Add a Brewfile to track binary dependencies
Add site setting for category of topics created by embedding
copyediting on topnav tooltips
/top tooltip clarification
omit needless words
BUGFIX: PMs could be created with a category

BUGFIX: hide category column when displaying the list of private messages
Merge pull request #1857 from velesin/qunit_not_assertion

Adds new QUnit assertion ("not") complementary to built-in "ok"
Merge pull request #1856 from velesin/search_controller_tests

Adds unit tests for SearchController
Allow using the API when Login required site setting is on.
Merge pull request #1861 from slainer68/login_required_allow_api

Allow to use the API when Login required site setting is on
BUGFIX: view latest topics should point to /latest and not /
BUGFIX: taller keyboard shortcuts modal to prevent then scrollbar