Custom assertion that writes out to the Crash Report. Based on an article by Mike Ash (http://www.mikeash.com/pyblog/friday-qa-2013-05-03-proper-use-of-asserts.html?utm_source=iOS+Dev+Weekly&utm_campaign=7dba454803-iOS_Dev_Weekly_Issue_93&utm_medium=email&utm_term=0_7bda94b7ca-7dba454803-267010305)