move isolated resources into fixtures module
s/isolated_*/fixtures/g
make client and url test api more friendly
clean up imports
start writing association scenarios
improve logging and assertion messages
cleanup methods in response helper

remove functions no longer used, reoder functions logically
standardize url naming convention
some resources return 400 instead of 404 on nonexistant error
write more scenarios for association and dissociation
replace old tests by scenarios in line_extension
replace old tests by scenarios in user_line