added a big picture summary to Changes file
fixing crabgrass_media tests and adding temp_file_test

* use require_relative
* String.chars.any? not String.present? - because AS might not be around.
* new test for temp files
run GC to make sure no old tempfiles are around

These were named the same way the new ones were and cleaning them up during the next test would cause the new files to disappear
use FactoryGirl for assets