Improve Xcode and CLT installation instructions.
mongodb: use 2.5.3 by default on Mavericks.
logstash 1.2.2

Closes #23474.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
selenium-server-standalone 2.37.0

Closes #23485.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
youtube-dl 2013.10.23.2

Closes #23492.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>
test_formula: use different/consistent SHA-1.
test_formula: add Mavericks bottles.
test_utils: fix Mavericks arch test.